FortiOS 6 – Anti-spam filter

Anti-spam filter

This section describes how to configure FortiGate email filtering for IMAP, POP3, and SMTP email. Email filtering includes both spam filtering and filtering for any words or files you want to disallow in email messages. If your FortiGate unit supports SSL content scanning and inspection, you can also configure spam filtering for IMAPS, POP3S, and SMTPS email traffic.

The Anti-Spam security profile is only available when operating the FortiGate in proxy-based inspection.

The following topics are included in this section:

Anti-spam concepts

Anti-spam techniques

Configuring Anti-spam

Order of spam filtering

Spam actions

Anti-spam examples

Anti-spam concepts

You can configure the FortiGate unit to manage unsolicited commercial email by detecting and identifying spam messages from known or suspected spam servers.

The FortiGuard Anti-Spam service uses both a sender IP reputation database and a spam signature database, along with sophisticated spam filtering tools, to detect and block a wide range of spam messages. Using FortiGuard Anti-Spam profile settings, you can opt to filter with IP address checking, URL checking, email checksum checking, detection of phishing URLs in email, and spam submission. Updates to the IP reputation and spam signature databases are provided continuously via the global FortiGuard Distribution Network.

At the FortiGuard Anti-Spam service page on the FortiGuard Labs website, you can find out whether an IP address is blacklisted in the FortiGuard Anti-Spam IP reputation database, or whether a URL or email address is in the signature database.

Anti-spam techniques

The FortiGate unit has a number of techniques available to help detect spam. Some use the FortiGuard AntiSpam service and require a subscription. The remainder use your DNS servers or use lists that you must maintain.

Black white list

These are the types of black white lists available. They include:

IP/Netmask

The FortiGate unit compares the IP address of the client delivering the email to the addresses in the IP address techniques

black / white list specified in the email filter profile. If a match is found, the FortiGate unit will take the action configured for the matching black / white list entry against all delivered email.

The default setting of the smtp-spamhdrip CLI command is disable. If enabled, the FortiGate unit will check all the IP addresses in the header of SMTP email against the specified IP address black / white list.

Email Wildcard

The FortiGate unit compares the sender email address, as shown in the message header and envelope MAIL FROM, to the pattern in the patterned field. The wildcard symbol is used in the place of characters in the address that may vary from the pattern. If a match is found, the FortiGate unit will take the action configured for the matching black / white list entry. l Email Regular Expression

The FortiGate unit compares the sender email address, as shown in the message envelope MAIL FROM, to the pattern in the patterned field. The regular expression that can be used is much more sophisticated than a simple wildcard variable. If a match is found, the FortiGate unit will take the action configured for the matching black/white list entry.

Pattern

The pattern field is for entering the identifying information that will enable the filter to correctly identify the email messages.

If the type is IP/Netmask the filter will be an IP address with a subnet mask.
If the type is Email Wildcard the filter will be an email address with a wildcard symbol in place of the variable characters. For example *.example.com or fred@*.com.
If the type is Email Regular Expression, regular expression can be used to create a more granular filter for email addresses. For example, ^[_a-z0-9-]+(\.[_a-z0-9-]+)*@(example|xmple|examp).(com|org|net) could be used filter based on a number of combinations of email domain names. Action
Tag

If this is the selected action, the email will be allowed through but it will be tagged with an indicator that clearly marks the email as spam. l Pass

If this is the selected action, the email will be allowed to go through to its destination on the assumption that the message is not spam.

Discard

If this is the selected action, the email will be dropped at the before reaching its destination. Status

Indicates whether this particular list is enabled or disabled.

Banned word check

When you enable banned word checking, your FortiGate unit will examine the email message for words appearing in the banned word list specified in the Anti-Spam profile. If the total score of the banned word discovered in the email message exceeds the threshold value set in the Anti-Spam profile, your FortiGate unit will treat the message as spam.

When determining the banned word score total for an email message, each banned word score is added once no matter how many times the word appears in the message. Use the command config spamfilter bword to Anti-spam techniques

add an email banned word list. Use the command config spamfilter profile to add a banned word list to an Anti-Spam profile.

How content is evaluated

Every time the banned word filter detects a pattern in an email message, it adds the pattern score to the sum of scores for the message. You set this score when you create a new pattern to block content. The score can be any number from zero to 99999. Higher scores indicate more offensive content. When the total score equals or exceeds the threshold, the email message is considered as spam and treated according to the spam action configured in the email filter profile. The score for each pattern is counted only once, even if that pattern appears many times in the email message. The default score for banned word patterns is 10 and the default threshold is 10. This means that by default, an email message is blocked by a single match.

A pattern can be part of a word, a whole word, or a phrase. Multiple words entered as a pattern are treated as a phrase. The phrase must appear as entered to match. You can also use wildcards or regular expressions to have a pattern match multiple words or phrases.

For example, the FortiGate unit scans an email message that contains only this sentence: “The score for each word or phrase is counted only once, even if that word or phrase appears many times in the email message.”

Banned word pattern	Pattern type	Assigned score	Score added to the sum for the entire page	Comment
word	Wildcard	20	20	The pattern appears twice but multiple occurrences are only counted once.
word phrase	Wildcard	20	0	Although each word in the phrase appears in the message, the words do not appear together as they do in the pattern. There are no matches.
word*phrase	Wildcard	20	20	The wildcard represents any number of any character. A match occurs as long as “word” appears before “phrase” regardless of what is in between them.
mail*age	Wildcard	20	20	Since the wildcard character can represent any characters, this pattern is a match because “email message” appears in the message.

In this example, the message is treated as spam if the banned word threshold is set to 60 or less.

Adding words to a banned word list

When you enter a word, set the Pattern-type to wildcards or regular expressions.

Wildcard uses an asterisk (“*”) to match any number of any character. For example, re* will match all words starting with “re”.

Regular expression uses Perl regular expression syntax. See http://perldoc.perl.org/perlretut.html for detailed information about using Perl regular expressions.

techniques

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FortiOS 6 – Application Control

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Application control

Using the Application Control Security Profiles feature, your FortiGate unit can detect and take action against network traffic depending on the application generating the traffic. Based on FortiGate Intrusion Protection protocol decoders, application control is a user-friendly and powerful way to use Intrusion Protection features to log and manage the behavior of application traffic passing through the FortiGate unit. Application control uses IPS protocol decoders that can analyze network traffic to detect application traffic even if the traffic uses nonstandard ports or protocols. Application control supports detection for traffic using HTTP protocol (versions 1.0, 1.1, and 2.0).

The FortiGate unit can recognize the network traffic generated by a large number of applications. You can create application control sensors that specify the action to take with the traffic of the applications you need to manage and the network on which they are active, and then add application control sensors to the firewall policies that control the network traffic you need to monitor.

Fortinet is constantly adding to the list of applications detected through maintenance of the FortiGuard Application Control Database. This database is part of the FortiGuard Intrusion Protection System Database because intrusion protection protocol decoders are used for application control and both of these databases have the same version number.

Cloud Access Security Inspection (CASI) is merged with Application Control resulting in changes to the GUI and the CLI.

You can identify the version of the application control database installed on your unit by going to the Licenses widget on the Dashboard and hovering over the IPS & Application Control line; the status, expiry date, and version will be displayed. Additionally, you can see the complete list of applications supported by FortiGuard Application Control on the FortiGuard site or http://fortiguard.com/appcontrol. This web page lists all of the supported applications. You can select any application name to see details about the application.

Application Control is a standard part of any FortiCare support contract and the database for Application Control signatures is separate from the IPS database. However, botnet application signatures are still part of the IPS signature database since these are more closely related with security issues and less about application detection.

This Handbook chapter includes Inside FortiOS: Application Control and provides readers an overview of the features and benefits of key FortiOS 5.6 components. For readers needing to delve into greater detail, we provide the following topics:

Application control concepts

Enabling application control in profile-based modes

Application control actions Application considerations

Application control monitor

Application control examples

Application control concepts

You can control network traffic generally by the source or destination address, or by the port, the quantity or similar attributes of the traffic itself in the security policy. If you want to control the flow of traffic from a specific application, these methods may not be sufficient to precisely define the traffic. To address this problem, the application control feature examines the traffic itself for signatures unique to the application generating it. Application control does not require knowledge of any server addresses or ports. The FortiGate unit includes signatures for over 2,000 applications, services, and protocols.

Updated and new application signatures are delivered to your FortiGate unit as part of your FortiGuard Application Control Service subscription, which is a free service. Fortinet is constantly increasing the number of applications that this feature can detect by adding applications to the FortiGuard Application Control Database. Because intrusion protection protocol decoders are used for application control, the application control database is part of the FortiGuard Intrusion Protection System Database. Both of these databases have the same version number.

You can find the version of the application control database installed on your unit by going to the Licenses widget on the Dashboard and hovering over the IPS& Application Control line; the status, expiry date, and version will be displayed.

To see the complete list of applications supported by FortiGuard Application Control go to the FortiGuard site or http://fortiguard.com/appcontrol. This web page lists all of the supported applications. You can select any application name to see details about the application.

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FortiOS 6 – DNS Filter

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DNS filter

You can configure DNS web filtering to allow, block, or monitor access to web content according to FortiGuard categories. When DNS web filtering is enabled, your FortiGate must use the FortiGuard DNS service for DNS lookups. DNS lookup requests sent to the FortiGuard DNS service return with an IP address and a domain rating that includes the FortiGuard category of the web page.

If that FortiGuard category is set to block, the result of the DNS lookup is not returned to the requester. If the category is set to redirect, then the address returned to the requester points at a FortiGuard redirect page.

You can also allow or monitor access based on FortiGuard category.

Blocking DNS requests to known botnet command & control addresses

FortiGuard maintains a database containing a list of known botnet command and control (C&C) addresses. This database is updated dynamically and stored on the FortiGate and requires a valid FortiGuard AntiVirus subscription.

When you block DNS requests to known botnet C&C addresses, using IPS, DNS lookups are checked against the botnet C&C database. All matching DNS lookups are blocked. Matching uses a reverse prefix match, so all subdomains are also blocked.

To enable this feature, go to Security Profiles > DNS Filter, and enable Block DNS requests to known botnet C&C.

Static Domain Filter

The DNS Static Domain Filter allows you to block, exempt, or monitor DNS requests by using IPS to look inside DNS packets and match the domain being looked up with the domains on the static URL filter list. If there is a match the DNS request can be blocked, exempted, monitored, or allowed.

If blocked, the DNS request is blocked and so the user cannot look up the address and connect to the site.

If exempted, access to the site is allowed even if another method is used to block it.

CLI commands

l Rename webfilter-sdns-server-ip and webfilter-sdns-server-port:

config system fortiguard set sdns-server-ip x.x.x.x set sdns-server-port 53

end l Configure DNS domain filter lists in order to decide access for specific domains:

config dnsfilter domain-filter edit {id} set id {integer} set name {string} set comment {string} config entries edit {id}

DNS

set id {integer} set domain {string} set type {simple | regex | wildcard} set action {block | allow | monitor} set status {enable | disable}

end

config dnsfilter profile edit “dns_profile1″ set comment ” config domain-filter set domain-filter-table <id>

set external-blocklist [addr1] [addr2] [addr3]

end config ftgd-dns config filters

edit 1 set category 49 set action block set log enable

next edit 2 set category 71 set action monitor set log enable

end

set log-all-url disable set block-action redirect set redirect-portal 0.0.0.0 set block-botnet enable

end l Configure DNS profile in a firewall policy:

config firewall policy edit 1 set srcintf “any” set dstintf “any” set srcaddr “all” set dstaddr “all” set action accept set schedule “always” set service “FTP” set utm-status enable set dnsfilter-profile “dns_profile1” set profile-protocol-options “default”

set nat enable

next end

Configure DNS profile in profile group:

config firewall profile-group edit “pgrp1” set dnsfilter-profile “dns_profile1” set profile-protocol-options “default”

end

DNS profile supports safe search

Users can take advantage of pre-defined DNS filter rules to edit DNS profiles and provide safe search for Google, Bing, and YouTube.

To add safe search to a DNS profile – GUI

Go to Security Profiles > DNS Filter.
Edit the default filter or create a new one.
Enable Enforce ‘Safe Search’ on Google, Bing, YouTube.
Select Strict or Moderate level for Restrict YouTube Access.

To add safe search to a DNS profile – CLI

config dnsfilter profile edit “default” set safe-search enable

set youtube-restrict {strict | moderate} (only available if safe-search enabled)

end

FortiGuard botnet protection

Preventing botnets from controlling your system is achieved by detecting and blocking connection attempts to known botnets. This feature also blocks connections to known phishing sites. The FortiGuard database is continually updated with addresses of known Command and Control (C&C) sites that botnet clients attempt to connect to, as well as a addresses of known phishing URLs.

To enable botnet and phishing protection in a DNS Filter profile, enable Block DNS requests to known botnet C&C.

The latest botnet database is available from FortiGuard. To see the version of the database and display its contents, go to System > FortiGuard > AntiVirus and view the lists for Botnet IPs and Botnet Domains.

You can block, monitor, or allow outgoing connections to botnet sites for each FortiGate interface.

FortiOS 6 – Web Filtering

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Web filter

This section describes FortiGate web filtering for HTTP traffic. The three main parts of the web filtering function, the Web Content Filter, the URL Filter, and the FortiGuard Web Filtering Service interact with each other to provide maximum control over what users on your network can view as well as protection to your network from many Internet content threats. Web Content Filter blocks web pages containing words or patterns that you specify. URL filtering uses URLs and URL patterns to block or exempt web pages from specific sources. FortiGuard Web Filtering provides many additional categories you can use to filter web traffic.

This Handbook chapter includes Inside FortiOS: Web Filtering and provides readers an overview of the features and benefits of key FortiOS 5.6 components.

For further detail than the Inside FortiOS document, we provide the following topics:

Web filter concepts

Inspection modes

FortiGuard Web Filtering Service

Configuring web filter profiles

Overriding FortiGuard website categorization

Using cookies to authenticate users in a Web Filter override

Web Profile Overrides

SafeSearch

YouTube Education Filter

Static URL filter

Web content filter

Web filtering example

Advanced web filter configurations

Web filter concepts

Web filtering is a means of controlling the content that an Internet user is able to view. With the popularity of web applications, the need to monitor and control web access is becoming a key component of secure content management systems that employ antivirus, web filtering, and messaging security. Important reasons for controlling web content include:

lost productivity because employees are accessing the web for non-business reasons l network congestion — when valuable bandwidth is used for non-business purposes, legitimate business applications suffer
loss or exposure of confidential information through chat sites, non-approved email systems, instant messaging, and peer-to-peer file sharing
increased exposure to web-based threats as employees surf non-business-related web sites l legal liability when employees access/download inappropriate and offensive material l copyright infringement caused by employees downloading and/or distributing copyrighted material.

Web filter concepts

As the number and severity of threats increase on the World Wide Web, the risk potential increases within a company’s network as well. Casual non-business related web surfing has caused many businesses countless hours of legal litigation as hostile environments have been created by employees who download and view offensive content. Web-based attacks and threats are also becoming increasingly sophisticated. Threats and web-based applications that cause additional problems for corporations include:

spyware/grayware l phishing l pharming l instant messaging l peer-to-peer file sharing l streaming media l blended network attacks.

Spyware, also known as grayware, is a type of computer program that attaches itself to a user’s operating system. It does this without the user’s consent or knowledge. It usually ends up on a computer because of something the user does such as clicking on a button in a pop-up window. Spyware can track the user’s Internet usage, cause unwanted pop-up windows, and even direct the user to a host web site. For further information, visit the FortiGuard Center.

Some of the most common types of grayware infection occur when:

downloading shareware, freeware, or other forms of file-sharing services l clicking on pop-up advertising l visiting legitimate web sites infected with grayware.

Phishing is the term used to describe attacks that use web technology to trick users into revealing personal or financial information. Phishing attacks use web sites and email that claim to be from legitimate financial institutions to trick the viewer into believing that they are legitimate. Although phishing is initiated by spam email, getting the user to access the attacker’s web site is always the next step.

Pharming is a next generation threat that is designed to identify and extract financial, and other key pieces of information for identity theft. Pharming is much more dangerous than phishing because it is designed to be completely hidden from the end user. Unlike phishing attacks that send out spam email requiring the user to click to a fraudulent URL, pharming attacks require no action from the user outside of their regular web surfing activities. Pharming attacks succeed by redirecting users from legitimate web sites to similar fraudulent web sites that have been created to look and feel like the authentic web site.

Instant messaging presents a number of problems. Instant messaging can be used to infect computers with spyware and viruses. Phishing attacks can be made using instant messaging. There is also a danger that employees may use instant messaging to release sensitive information to an outsider.

Peer-to-peer (P2P) networks are used for file sharing. Such files may contain viruses. Peer-to-peer applications take up valuable network resources and may lower employee productivity but also have legal implications with the downloading of copyrighted or sensitive company material.

Streaming media is a method of delivering multimedia, usually in the form of audio or video to Internet users. Viewing streaming media impacts legitimate business by using valuable bandwidth.

Blended network threats are rising and the sophistication of network threats is increasing with each new attack. Attackers learn from each successful attack and enhance and update their attack code to become more dangerous and to spread faster. Blended attacks use a combination of methods to spread and cause damage. Using virus or network worm techniques combined with known system vulnerabilities, blended threats can quickly Web filter concepts

spread through email, web sites, and Trojan applications. Examples of blended threats include Nimda, Code Red, Slammer, and Blaster. Blended attacks can be designed to perform different types of attacks, which include disrupting network services, destroying or stealing information, and installing stealthy backdoor applications to grant remote access.

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FortiOS 6 – AntiVirus

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AntiVirus

This section describes how to configure the antivirus options. From an antivirus profile you can configure the

FortiGate unit to apply antivirus protection to HTTP, FTP, IMAP, POP3, SMTP, and NNTP sessions. If your FortiGate unit supports SSL/SSH content scanning and inspection, you can also configure antivirus protection for HTTPS, IMAPS, POP3S, SMTPS, and FTPS sessions.

In many cases you can just customize the default antivirus profile and apply it to the security policy that accepts the traffic to be virus scanned. You can also create custom antivirus profiles if want to apply different types of virus protection to different traffic.

This Handbook chapter includes Inside FortiOS: AntiVirus providing readers an overview of the features and benefits of key FortiOS 5.6 components.

For readers needing to delve into greater detail, we provide the following topics:

l Antivirus concepts l Enabling AntiVirus scanning l Testing your antivirus configuration l Example Scenarios

Antivirus concepts

The word “antivirus” refers to a group of features that are designed to prevent unwanted and potentially malicious files from entering your network. These features all work in different ways, which include checking for a file size, name, or type, or for the presence of a virus or grayware signature.

The antivirus scanning routines your FortiGate unit uses are designed to share access to the network traffic. This way, each individual feature does not have to examine the network traffic as a separate operation, and the overhead is reduced significantly. For example, if you enable file filtering and virus scanning, the resources used to complete these tasks are only slightly greater than enabling virus scanning alone. Two features do not require twice the resources.

Antivirus scanning examines files for viruses, worms, trojans, and other malware. The antivirus scan engine has a database of virus signatures it uses to identify infections. If the scanner finds a signature in a file, it determines that the file is infected and takes the appropriate action.

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FortiOS 6 – Inspection Modes

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Inspection modes

You can select one of two inspection modes from the System > Settings page to control the security profile inspection mode for your FortiGate or VDOM.

Proxy-based inspection, that reconstructs content passing through the FortiGate unit and inspects the content for security threats, or
Flow-based inspection, that takes a snapshot of content packets and uses pattern matching to identify security threats in the content.

Each inspection component plays a role in the processing of traffic en route to its destination. Having control over flow and proxy mode is helpful if you want to be sure that only flow inspection mode is used (and that proxy inspection mode is not used). In most cases proxy mode is preferred because more security profile features are available and more configuration options for these individual features are available. Yet, some implementations may require all security profile scanning to only use flow mode. In this case, you can set your FortiGate to flow mode knowing that proxy mode inspection will not be used. While both modes offer significant security, proxybased provides more features and flow-based is designed to optimize performance.

This section addresses the following topics:

Proxy-based inspection

Flow-based inspection

Changing between proxy and flow mode

Comparison of inspection types

Proxy-based inspection

If a FortiGate or VDOM is configured for proxy-based inspection, then a mixture of flow-based and proxy-based inspection occurs. Traffic initially encounters the IPS engine, which applies single-pass IPS, Application Control, and CASI, if configured in the firewall policy accepting the traffic.

The traffic is then sent for proxy-based inspection. Proxy-based inspection extracts and caches content, such as files and web pages, from a content session and inspects the cached content for threats. Content inspection takes place in the following order: VoIP inspection, DLP, AntiSpam, Web Filtering, AntiVirus, and ICAP.

If no threat is found, the proxy relays the content to its destination. If a threat is found, the proxy can block the threat and send a replacement message in its stead. The proxy can also block VoIP traffic that contains threats.

Transparent web proxy mode

In proxy mode, FortiOS 5.6 functions just like FortiOS 5.4 with the addition of the new Transparent Web Proxy mode. See New Operating mode for Transparent web proxy in What’s New in FortiOS 5.6.

Flow-based inspection

Flow-based inspection identifies and blocks security threats in real time as they are identified using single-pass Direct Filter Approach (DFA) pattern matching to identify possible attacks or threats.

If a FortiGate or a VDOM is configured for flow-based inspection, depending on the options selected in the firewall policy that accepted the session, flow-based inspection can apply IPS, Application Control, Web Filtering, DLP, and AntiVirus. Flow-based inspection is all done by the IPS engine and, as you would expect, no proxying is involved.

All of the applicable flow-based security modules are applied simultaneously in one single pass, and pattern matching is offloaded and accelerated by CP8 or CP9 processors. IPS, Application Control, flow-based Web Filtering, and flow-based DLP filtering happen together. Flow-based AntiVirus scanning caches files during protocol decoding and submits cached files for virus scanning while the other matching is carried out.

Flow-based inspection typically requires fewer processing resources than proxy-based inspection and does not change packets, unless a threat is found and packets are blocked. Flow-based inspection cannot apply as many features as proxy inspection. For example, flow-based inspection does not support client comforting and some aspects of replacement messages.

In FortiOS 5.6, flow-based inspection requires the new NGFW mode.

Changing between proxy and flow mode

You can see which inspection mode your FortiGate is using by looking at the System Information widget on your Dashboard.

To change inspection modes, go to System > Settings and scroll down to Inspection Mode. You can select Flow-based to operate in Flow mode or Proxy to operate in Proxy mode.

When you select Flow-based, all proxy mode profiles are converted to flow mode, removing any proxy settings. As well proxy mode only features (for example, Web Application Profile) are removed from the GUI.

In addition, selecting Flow-based inspection will cause the Explicit Web Proxy and Explicit FTP Proxy features to be removed from the GUI and the CLI. This includes Explicit Proxy firewall policies.

W hen you select Flow-based you can only configure Virtual Servers (under Policy & Objects > Virtual Servers) with Type set to HTTP, TCP, UDP, or IP.

If required, you can change back to proxy mode through the System > Settings page.

If your FortiGate has multiple VDOMs, you can set the inspection mode independently for each VDOM. Use the top left drop-down menu to go to Global > System > VDOM. Click Editfor the VDOM you wish to change and select the Inspection Mode.

From the GUI, you can only configure antivirus and web filter security profiles in proxy mode. From the CLI you can configure flow-based antivirus profiles, web filter profiles and DLP profiles and they will appear on the GUI and include their inspection mode setting. Also, flow-based profiles created when in flow mode are still available when you switch to proxy mode.

NGFW profile-based and NGFW policy-based modes

When you select Flow-based as the Inspection Mode, you have the option in FortiOS 5.6 to select an NGFW Mode. NGFW Profile-based mode works the same as flow-based mode did in FortiOS 5.4

When selecting NGFW policy-based mode you can also select the SSL/SSH Inspection mode that is applied to all policies.

In the new NGFW Policy-based mode, you add applications and web filtering profiles directly to a policy without having to first create and configure Application Control or Web Filtering profiles. See NGFW Policy Mode on page

When you change to flow-based inspection, all proxy mode profiles are converted to flow mode, removing any proxy settings. And proxy-mode only features (for example, Web Application Profile) are removed from the GUI.

If your FortiGate has multiple VDOMs, you can set the inspection mode independently for each VDOM. Go to System > VDOM. Click Edit for the VDOM you wish to change and select the Inspection Mode. CLI syntax

The following CLI commands can be used to configure inspection and NGFW (called “policy” in the CLI) modes:

config system settings set inspection-mode {proxy | flow} set policy-mode {standard | ngfw}

end

Comparison of inspection types

The tables in this section show how different security features map to different inspection types and present the strengths and weaknesses of proxy- vs. flow-based inspection.

Security profile features mapped to inspection mode

The table below lists FortiOS security profile features and shows whether they are available in flow-based or proxy-based inspection modes.

Security Profile Feature	Flow-based inspection	Proxy-based inspection
AntiVirus	x	x
Web Filter	x	x

Security Profile Feature	Flow-based inspection	Proxy-based inspection
DNS Filter	x	x
Application Control	x	x
Intrusion Protection	x	x
Anti-Spam		x
Data Leak Protection		x
VoIP		x
ICAP		x
Web Application Firewall		x
FortiClient Profiles	x	x
Proxy Options	x	x
SSL Inspection	x	x
SSH Inspection		x
Web Rating Overrides	x	x
Web Profile Overrides		x

Individual security profile considerations

In flow mode, AntiVirus and Web Filter profiles only include flow-mode features. Web filtering and virus scanning are still done with the same engines and to the same accuracy, but some inspection options are limited or not available in flow mode. Application control, intrusion protection, and FortiClient profiles are not affected when switching between flow and proxy mode.

Application control uses flow-based inspection; if you apply an additional security profile to your traffic that is proxy-based, the connection will simply timeout rather than display the warning, or replacement, message. However, Application Control will still function.

Even though VoIP profiles are not available from the GUI in flow mode, the FortiGate can process VoIP traffic. In this case the appropriate session helper is used (for example, the SIP session helper).

Setting flow or proxy mode doesn’t change the settings available from the CLI. However, when in flow mode you can’t save security profiles that are set to proxy mode.

You can also add proxy-only security profiles to firewall policies from the CLI. So, for example, you can add a VoIP profile to a security policy that accepts VoIP traffic. This practice isn’t recommended because the setting will not be visible from the GUI.

If you set flow-based to use external servers for FortiWeb and FortiMail you must use the CLI to set a Web Application Firewall profile or Anti-Spam profile to external mode and add the Web Application Firewall profile or AntiSpam profile to a firewall policy.

Proxy mode and flow mode antivirus and web filter profile options

The following tables list the antivirus and web filter profile options available in proxy and flow modes.

Antivirus features in proxy and flow mode

Feature	Proxy	Flow
Scan Mode (Quick or Full)	no	yes
Detect viruses (Block or Monitor)	yes	yes
Inspected protocols	yes	no (all relevant protocols are inspected)
Inspection Options	yes	yes (not available for quick scan mode)
Treat Windows Executables in Email Attachments as Viruses	yes	yes
Send Files to FortiSandbox Appliance for Inspection	yes	yes
Use FortiSandbox Database	yes	yes
Include Mobile Malware Protection	yes	yes

Web filter features in proxy and flow mode

Feature	Proxy	Flow
FortiGuard category based filter	yes	yes (show, allow, monitor, block)
Category Usage Quota	yes	no
Allow users to override blocked categories (on some models)	yes	no
Search Engines	yes	no

Feature		Proxy Flow
	Enforce ‘Safe Search’ on Google, Yahoo!, Bing, Yandex	yes	no
	Restrict YouTube Access	yes	no
	Log all search keywords	yes	no
Static URL Filter		yes	yes
	Block invalid URLs	yes	no
	URL Filter	yes	yes
	Block malicious URLs discovered by FortiSandbox	yes	yes
	Web Content Filter	yes	yes
Rating Options		yes	yes
	Allow websites when a rating error occurs	yes	yes
	Rate URLs by domain and IP Address	yes	yes
	Block HTTP redirects by rating	yes	no
	Rate images by URL	yes	no
Proxy Options		yes	no
	Restrict Google account usage to specific domains	yes	no
	Provide details for blocked HTTP 4xx and 5xx errors	yes	no
	HTTP POST Action	yes	no
	Remove Java Applets	yes	no
	Remove ActiveX	yes	no
	Remove Cookies	yes	no
	Filter Per-User Black/White List	yes	no

AntiVirus scanning differences between versions of FortiOS 5.x

In FortiOS 5.0, 5.2, 5.4, 5.6 and 6.0, there are several AntiVirus (AV) scanning inspection modes available. FortiOS 5.0 includes proxy and flow-based virus scanning. FortiOS 5.2 also uses proxy-based and flowbased scanning, but the flow-based mode in FortiOS 5.2 uses a new approach to flow-based scanning (that is sometimes called deepflow or deep flow scanning). FortiOS 5.4 and onward offer another flow-based mode, quick mode, to inspect traffic efficiently.

The databases used for AV scanning does not change from proxy to flow mode unless quick mode is enabled. In flow-based quick mode, a compact antivirus database is used.

AntiVirus scanning examines files in HTTP, HTTPS, email, and FTP traffic for threats as they pass through your FortiGate. If the traffic contains compressed files, they are also examined. Go to the SysAdmin Note on the Fortinet Cookbook site for detailed information on supported compression formats in antivirus scanning.

If the AV scanner finds a threat such as a virus or some other malware, FortiOS protects your network by blocking the file.

FortiOS includes a number of AntiVirus features that make virus scanning more user-friendly. One of these features, called replacement messages, sends a customizable message to anyone whose file is blocked by AV scanning, to explain what happened and why. Other features make communication between the client and the server more seamless. The availability of these changes depending on the inspection mode.

Proxy-based AV scanning

Proxy-based AV scanning is the most feature-rich AV scanning mode. This mode uses a proxy to manage the communication between client and server. The proxy extracts content packets from the data stream as they arrive and buffers the content until the complete file is assembled. Once the file is whole, the AV scanner examines the file for threats. If no threats are found, the file is sent to its destination. If a threat is found, the file is blocked.

Because proxy-based scanning is applied to complete files, including compressed files, it provides very effective threat detection. Proxy-based scanning also supports a full range of features, including replacement messages and client comforting, making proxy-based scanning the most user friendly inspection mode. In addition the proxy manages the communication between the client and the server, improving the user experience. For example, in flow mode if a virus is found, the last part of the file is not downloaded and the connection just times out and the user cannot tell what is going on. In proxy mode, the users gets a message about the file being blocked.

Proxy-based scanning inspects all files under the oversized threshold. Since the FortiGate unit has a limited amount of memory, files larger than a certain size do not fit within the memory buffer. The default buffer size is 10 MB. You can use the uncompsizelimitCLI command to adjust the size of this memory buffer. Files larger than the threshold are passed to the destination without scanning. You can use the Oversized File/Email setting in Security Profiles > Proxy Options to block files larger than the antivirus buffer if allowing files that are too large to be scanned is an unacceptable security risk.

During the buffering and scanning procedure, the client must wait. With a default configuration, the file is released to the client only after it is scanned. You can enable client comforting in the Proxy Options security profile to feed the client a trickle of data to prevent them from possibly thinking the transfer is stalled and consequently canceling the download.

Flow-based AV scanning

Although the name “flow-based scanning” is used in FortiOS 5.0, 5.2, 5.4, and 5.6, the different versions handle this mode in very different ways.

Flow AV in FortiOS 5.4 and 5.6

In FortiOS 5.4 and 5.6, there are two modes available for flow-based virus scanning: Quick and Full scan mode. Full mode is the same as flow-based scanning in FortiOS 5.2 (see below). Quick mode uses a compact antivirus database and advanced techniques to improve performance. You can designate quick or full scan mode when configuring the antivirus profile in the GUI. Alternatively, use the following CLI command to enable quick or full mode:

config antivirus profile edit <profile> set scan-mode {quick | full}

end

Flow AV in FortiOS 5.2 (deepflow or deep flow)

FortiOS 5.2 introduced a new type of flow-based AV scanning, that is sometimes called deepflow or deep flow, and that takes a hybrid approach where content packets are buffered while simultaneously being sent to their destination. When all of the files packets have been collected and buffered, but before the final packet is delivered, the buffered file is scanned. If a threat is found, the last packet is blocked and the client application has to deal with not getting the completed file. If no threat is found the final packet is sent and the user gets their file.

Deepflow AV scanning is as good as proxy-based AV scanning at detecting threats. There may be a small performance advantage over proxy-based AV as files get larger based on the difference between sending the whole file after analysis and just sending the last packet. Deepflow’s most notable limitation is that, just like the flow-based AV in 5.0, it does not support many of the user-friendly features provided by proxy-based AV.

Flow AV in FortiOS 5.0

In FortiOS 5.0, flow-based AV scanning examines the content of individual data packets as they pass through the FortiGate. There is no proxy involved so packets are not changed by the proxy and files are not buffered for analysis. Potentially less memory and CPU resources are used, resulting in a potential performance increase compared to using proxy-based mode. FortiOS 5.0 flow-based AV scanning is also not limited by file size.

Flow AV uses the IPS engine and the AV database and is effective at many kinds of threat detection; however, because it can only analyze what is in an individual packet rather than a complete file, flow-based scanning cannot detect some types of malware, including polymorphic code. Malware in documents, compressed files, and some archives are also less likely to be detected.

Flow AV does not actually block files, it stops delivering a file’s packets once a threat has been detected. This means that parts of the file may already have been delivered when the threat has been detected and the recipient application is responsible for dealing with the partially complete content.

In addition flow AV can be less user friendly. Replacement messages are not supported and clients may have to wait for sessions to time out without knowing why content has been blocked.

FortiOS 6 – Security profiles overview

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Security profiles overview

The FortiGate line combines a number of security features to protect your network from threats. As a whole, these features, when included in a single Fortinet security appliance, are referred to as Security Profiles.

This overview addresses the following topics:

l Traffic inspection l Content inspection and filtering l Security profile components l Security profiles/lists/sensors

Firewall policies limit access, and while this and similar features are a vital part of securing your network, they are not covered in this discussion of Security Profiles.

FortiOS 5.4 no longer supports FortiClient 5.0.

FortiOS 5.4.1 supports only FortiClient 5.4.1. Be sure to upgrade managed FortiClients before upgrading the FortiGate to 5.4.1.

FortiOS 5.2 can support FortiClient 5.0, but only if the FortiGate upgraded to FortiOS 5.2. Customers need to purchase a FortiClient 5.4 subscription-based FortiClient license.

Traffic inspection

When the FortiGate unit examines network traffic one packet at a time for IPS signatures, it is performing traffic analysis. This is unlike content analysis where the traffic is buffered until files, email messages, web pages, and other files are assembled and examined as a whole.

DoS policies use traffic analysis by keeping track of the type and quantity of packets, as well as their source and destination addresses.

Application control uses traffic analysis to determine which application generated the packet.

Although traffic inspection doesn’t involve taking packets and assembling files they are carrying, the packets themselves can be split into fragments as they pass from network to network. These fragments are reassembled by the FortiGate unit before examination.

No two networks are the same and few recommendations apply to all networks. This topic offers suggestions on how you can use the FortiGate unit to help secure your network against content threats.

IPS signatures

IPS signatures can detect malicious network traffic. For example, the Code Red worm attacked a vulnerability in the Microsoft IIS web server. Your FortiGate’s IPS system can detect traffic attempting to exploit this vulnerability. IPS may also detect when infected systems communicate with servers to receive instructions.

Traffic inspection

IPS recommendations

Enable IPS scanning at the network edge for all services. l Use FortiClient endpoint IPS scanning for protection against threats that get into your network.
Subscribe to FortiGuard IPS Updates and configure your FortiGate unit to receive push updates. This will ensure you receive new IPS signatures as soon as they are available.
Your FortiGate unit includes IPS signatures written to protect specific software titles from DoS attacks. Enable the signatures for the software you have installed and set the signature action to Block.
You can view these signatures by going to Security Profiles > Intrusion Prevention and selecting the [View IPS Signatures] link in the right-hand corner of the window. l Because it is critical to guard against attacks on services that you make available to the public, configure IPS signatures to block matching signatures. For example, if you have a web server, configure the action of web server signatures to Block.

Suspicious traffic attributes

Network traffic itself can be used as an attack vector or a means to probe a network before an attack. For example, SYN and FIN flags should never appear together in the same TCP packet. The SYN flag is used to initiate a TCP session while the FIN flag indicates the end of data transmission at the end of a TCP session.

The FortiGate unit has IPS signatures that recognize abnormal and suspicious traffic attributes. The SYN/FIN combination is one of the suspicious flag combinations detected in TCP traffic by the TCP.BAD.FLAGS signature.

The signatures that are created specifically to examine traffic options and settings, begin with the name of the traffic type they are associated with. For example, signatures created to examine TCP traffic have signature names starting with TCP.

Application control

While applications can often be blocked by the ports they use, application control allows convenient management of all supported applications, including those that do not use set ports. Application control recommendations

l Some applications behave in an unusual manner in regards to application control. For more information, see Application considerations on page 128. l By default, application control allows the applications not specified in the application control list. For high security networks, you may want to change this behavior so that only the explicitly allowed applications are permitted.

SSL/SSH inspection

Regular web filtering can be circumvented by using https:// instead of http://. By enabling this feature, the FortiGate can filter traffic that is using the HTTPS protocol. This sort of analysis is some times referred to as deep scanning.

Deep Inspection works along the following lines: If your FortiGate unit has the correct chipset it will be able to scan SSL encrypted traffic in the same way that regular traffic can be scanned. The FortiGate firewall will essentially receive the traffic on behalf of the client and open up the encrypted traffic. Once it is finished it reContent inspection and filtering

encrypts the traffic and sends it on to its intended recipient. It is very similar to a man-in-the-middle attack. By enabling this feature, it allows the FortiGate firewall to filter on traffic that is using the SSL encrypted protocol.

The encrypted protocols that can be inspected are:

HTTPS l SMTPS l POP3S l IMAPS l FTPS

Before the invention of SSL inspection, scanning regular web traffic can be circumvented by using the prefix https:// instead of http:// in the URL. SSL inspection prevents this circumvention. However, because when the encrypted traffic is decrypted it has to be re-encrypted with the FortiGate’s certificate rather than the original certificate it can cause errors because the name on the certificate does not match the name on the web site.

At one point deep inspection was something that was either turned on or off. Now individual deep inspection profiles can be created depending on the requirements of the policy. Depending on the Inspection Profile, you can:

Configure which CA certificate will be used to decrypt the SSL encrypted traffic. l Configure which SSL protocols will be inspected. l Configure which ports will be associated with which SSL protocols for the purpose of inspection.
Configure which websites will be exempt from SSL inspection l Configure whether or not to allow invalid SSL certificates. l Configure whether or not SSH traffic will be inspected.

Web rating overrides

This feature allows you to override the FortiGuard Web Filtering. This option allows users to change the rating for a website and control access to the site without affecting the rest of the sites in the original category. More information can be found in Overriding FortiGuard website categorization.

Web profile overrides

This feature allows administrators to grant temporary access to sites that are otherwise blocked by a web filter profile. The temporary access can be granted to a user, user group, or source IP address. The time limit can be set in days, hours, or minutes. See the section on Web Profile Overrides for more information.

Content inspection and filtering

When the FortiGate unit buffers the packets containing files, email messages, web pages, and other similar files for reassembly before examining them, it is performing content inspection. Traffic inspection, on the other hand, is accomplished by the FortiGate unit examining individual packets of network traffic as they are received.

No two networks are the same and few recommendations apply to all networks. This topic offers suggestions on how you can use the FortiGate unit to help secure your network against threats to content. Be sure to understand the effects of the changes before using the suggestions.

AntiVirus

The FortiGate antivirus scanner can detect viruses and other malicious payloads used to infect machines. The FortiGate unit performs deep content inspection. To prevent attempts to disguise viruses, the antivirus scanner will reassemble fragmented files and uncompress content that has been compressed. Patented Compact Pattern Recognition Language (CPRL) allows further inspection for common patterns, increasing detection rates of virus variations in the future.

AntiVirus recommendations

Enable antivirus scanning at the network edge for all services. l Use FortiClient endpoint antivirus scanning for protection against threats that get into your network.
Subscribe to FortiGuard AntiVirus Updates and configure your FortiGate unit to receive push updates. This will ensure that new antivirus signatures are loaded onto your FortiGate as soon as they are available.
Enable the Extended Virus Database if your FortiGate unit supports it.
Examine antivirus logs periodically. Take particular notice of repeated detections. For example, repeated virus detection in SMTP traffic could indicate a system on your network is infected and is attempting to contact other systems to spread the infection using a mass mailer.
To conserve system resources, avoid scanning email messages twice. Scan messages as they enter and leave your network or when clients send and retrieve them, rather than both.
Enable Treat Windows Executables in Email Attachments as Viruses if you are concerned about incoming ‘.exe’ files.

FortiGuard web filtering

The web is the most popular part of the Internet and, as a consequence, virtually every computer connected to the Internet is able to communicate using port 80, HTTP. Botnet communications take advantage of this open port and use it to communicate with infected computers. FortiGuard Web Filtering can help stop infections from malware sites and help prevent communication if an infection occurs. FortiGuard web filtering recommendations

Enable FortiGuard Web Filtering at the network edge. l Install the FortiClient application and use FortiGuard Web Filtering on any systems that bypass your FortiGate unit.
Block categories such as Pornography, Malware, Spyware, and Phishing. These categories are more likely to be dangerous.
In the Anti-Spam profile, enable Spam Detection and Filtering and then enable IP Address Check. Many IP addresses used in spam messages lead to malicious sites; checking them will protect your users and your network.

DNS filter

DNS-based web filtering

This feature is similar to the FortiGuard DNS web filtering available in FortiOS 5.2. You can configure DNS web filtering to allow, block, or monitor access to web content according to FortiGuard categories. When DNS web filtering is enabled, your FortiGate must use the FortiGuard DNS service for DNS lookups. DNS lookup requests Content inspection and filtering

sent to the FortiGuard DNS service return with an IP address and a domain rating that includes the FortiGuard category of the web page.

If that FortiGuard category is set to block, the result of the DNS lookup is not returned to the requester. If the category is set to redirect, then the address returned to the requester points at a FortiGuard redirect page.

You can also allow access or monitor access based on FortiGuard category.

The following filtering options can be configured in a DNS Filter security profile:

Blocking DNS requests to known Botnet C&C addresses

A new FortiGuard database contains a list of known Botnet C&C addresses. This database is updated dynamically and stored on the FortiGate. This database is covered by FortiGuard web filter licensing; you must have an active FortiGuard web filtering license to use this feature. You can view the botnet lists by going to System > FortiGuard > Botnet IPs and System > FortiGuard > Botnet Domains.

When you block DNS requests to known Botnet C&C addresses, using IPS, DNS lookups are checked against the Botnet C&C database. All matching DNS lookups are blocked. Matching uses a reverse prefix match, so all subdomains are also blocked.

To enable blocking of DNS requests to known Botnet C&C addresses, go to Security Profiles > DNS Filter, and enable Block DNS requests to known botnet C&C. When you do this in FortiOS 5.4.1, you can open a definitions window by clicking on “botnet package.”

Static URL filter

The DNS static URL filter allows you to block, exempt, or monitor DNS requests by using IPS to look inside DNS packets and match the domain being looked up with the domains on the static URL filter list. If there is a match the DNS request can be blocked, exempted, monitored, or allowed.

If blocked, the DNS request is blocked and so the user cannot look up the address and connect to the site.

If exempted, access to the site is allowed even if another method is used to block it.

Anti-Spam

Spam is a common means by which attacks are delivered. Users often open email attachments they should not, and infect their own machine. The FortiGate email filter can detect harmful spam and mark it, alerting the user to the potential danger.

Anti-Spam filter recommendations

l Subscribe to the FortiGuard Anti-Spam Filtering service. l Enable email filtering at the network edge for all types of email traffic. l Use FortiClient endpoint scanning for protection against threats that get into your network.

Data Leak Prevention

Most security features on the FortiGate unit are designed to keep unwanted traffic out of your network while Data Leak Prevention (DLP) can help you keep sensitive information from leaving your network. For example, credit card numbers and social security numbers can be detected by DLP sensors.

DLP recommendations

Rules related to HTTP posts can be created, but if the requirement is to block all HTTP posts, a better solution is to use application control or the HTTP POST Action option in the web filter profile.
While DLP can detect sensitive data, it is more efficient to block unnecessary communication channels than to use DLP to examine it. If you don’t use instant messaging or peer-to-peer communication in your organization, for example, use application control to block them entirely.

Security profile components

Below is a brief description of the security profiles and their features.

AntiVirus

Your FortiGate unit stores a virus signature database that can identify more than 15,000 individual viruses.

FortiGate models that support additional virus databases are able to identify hundreds of thousands of viruses. With a FortiGuard AntiVirus subscription, the signature databases are updated whenever a new threat is discovered.

AntiVirus also includes file filtering. When you specify files by type or by file name, the FortiGate unit will block the matching files from reaching your users.

FortiGate units with a hard drive or configured to use a FortiAnalyzer unit can store infected and blocked files for that you can examine later.

Web filter

Web filtering includes a number of features you can use to protect or limit your users’ activity on the web.

FortiGuard Web Filtering is a subscription service that allows you to limit access to web sites. More than 60 million web sites and two billion web pages are rated by category. You can choose to allow or block each of the 77 categories.

URL filtering can block your network users from access to URLs that you specify.

Web content filtering can restrict access to web pages based on words and phrases appearing on the web page itself. You can build lists of words and phrases, each with a score. When a web content list is selected in a web filter profile, you can specify a threshold. If a user attempts to load a web page and the score of the words on the page exceeds the threshold, the web page is blocked.

DNS filter

The FortiGate will inspect DNS traffic to any DNS server, so long as the policy has DNS inspection enabled. The

FortiGate will intercept DNS requests, regardless of the destination IP, and redirect it to the FortiGuard Secure

Security profile components

DNS server — this is separate from the FortiGuard DNS server.

The Secure DNS server will resolve and rate the FQDN and send a DNS response which includes both IP and rating of the FQDN back to the FortiGate, where it will handle the DNS response according to the DNS filter profile.

Application control

Although you can block the use of some applications by blocking the ports they use for communications, many applications do not use standard ports to communicate. Application control can detect the network traffic of more than 1,000 applications, improving your control over application communication.

Cloud Access Security Inspection (CASI)

This feature introduces a new security profile called Cloud Access Security Inspection (CASI) that provides support for fine-grained control on popular cloud applications, such as YouTube, Dropbox, Baidu, and Amazon. The CASI profile is applied to a policy much like any other security profile.

Unfortunately CASI does not work when using Proxy-based profiles for AV or Web filtering for example.

Make sure to only use Flow-based profiles in combination with CASI on a specific policy.

Intrusion protection

The FortiGate Intrusion Protection System (IPS) protects your network against hacking and other attempts to exploit vulnerabilities of your systems. More than 3,000 signatures are able to detect exploits against various operating systems, host types, protocols, and applications. These exploits can be stopped before they reach your internal network.

You can also write custom signatures tailored to your network.

Anti-spam

FortiGuard Anti-Spam is a subscription service that includes an IP address black list, a URL black list, and an email checksum database. These resources are updated whenever new spam messages are received, so you do not need to maintain any lists or databases to ensure accurate spam detection.

You can use your own IP address lists and email address lists to allow or deny addresses, based on your own needs and circumstances.

Data Leak Prevention

Data Leak Prevention (DLP) allows you to define the format of sensitive data. The FortiGate unit can then monitor network traffic and stop sensitive information from leaving your network. Rules for U.S. social security numbers, Canadian social insurance numbers, as well as Visa, Mastercard, and American Express card numbers are included.

profile components

VoIP

The Session Initiation Protocol (SIP) is an IETF application layer signaling protocol used for establishing, conducting, and terminating multi-user multimedia sessions over TCP/IP networks using any media. SIP is often used for Voice over IP (VoIP) calls but can be used for establishing streaming communication between end points.

For more information, see VoIP Solutions: SIP.

ICAP

This module allows for the offloading of certain processes to a separate server so that your FortiGate firewall can optimize its resources and maintain the best level of performance possible.

FortiClient profiles

FortiClient is an all-in-one comprehensive endpoint security solution that extends the power of Fortinet’s Advanced Threat Protection (ATP) to end user devices. As the endpoint is the ultimate destination for malware that is seeking credentials, network access, and sensitive information, ensuring that your endpoint security combines strong prevention with detection and mitigation is critical.

The FortiGate provides network security by defining compliance rules for FortiClient endpoints.

For more information, see the FortiClient 5.4.1 Administration Guide.

Proxy options

Proxy Options includes features you can configure for when your FortiGate is operating in proxy mode, including protocol port mapping, block oversized files/emails, and other web and email options.

SSL/SSH inspection

SSL/SSH Inspection (otherwise known as Deep Inspection) is used to scan HTTPS traffic in the same way that HTTP traffic can be scanned. This allows the FortiGate to receive and open up the encrypted traffic on behalf of the client, then the traffic is re-encrypted and sent on to its intended destination.

Individual Deep Inspection profiles can be created, depending on the requirements of the policy. Depending on the profile, you can:

l Configure which CA certificate will be used to decrypt the SSL encrypted traffic l Configure which SSL protocols will be inspected l Configure which ports will be associated with which SSL protocols for inspection l Configure whether or not to allow invalid SSL certificates l Configure whether or not SSH traffic will be inspected

Security profiles/lists/sensors

A profile is a group of settings that you can apply to one or more firewall policies. Each Security Profile feature is enabled and configured in a profile, list, or sensor. These are then selected in a security policy and the settings apply to all traffic matching the policy. For example, if you create an antivirus profile that enables antivirus scanning of HTTP traffic, and select the antivirus profile in the security policy that allows your users to access the World Wide Web, all of their web browsing traffic will be scanned for viruses.

Because you can use profiles in more than one security policy, you can configure one profile for the traffic types handled by a set of firewall policies requiring identical protection levels and types, rather than repeatedly configuring those same profile settings for each individual security policy.

For example, while traffic between trusted and untrusted networks might need strict protection, traffic between trusted internal addresses might need moderate protection. To provide the different levels of protection, you might configure two separate sets of profiles: one for traffic between trusted networks, and one for traffic between trusted and untrusted networks.

Inside FortiOS: Web Filtering

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Inside FortiOS: Web Filtering

A Web Filtering solution is designed to restrict or control the content a reader is authorized to access, delivered over the Internet via the Web browser. It may be used to improve security, prevent objectionable activities, and increase productive within an organization.

Intelligent and effective content control

Web-based threats such as Phishing, drive-by Malware sites, and Botnets are more sophisticated and scrutinized than ever, and as well as increasingly difficult to control due to the rise of mobility in the workplace, even more difficult for you to control. The Web has become the preferred medium of choice for hackers and thieves looking for new ways to disrupt services, steal information, and perform malicious activities for financial gain. In addition, employees who visit websites containing objectionable content can expose your organization to civil or criminal liability.

FortiOS Web Filtering solution utilizes three main components of the web filtering function: the Web Content Filter, the URL Filter, and the FortiGuard Web Filtering Service. These functions integrate with each other to provide maximum control over what the Internet user can view as well as protection to the network from many Internet content threats. Web Content Filtering blocks web pages containing words or patterns that you specify. URL filtering uses URLs and URL patterns to block or exempt web pages from specific sources. FortiGuard Web Filtering provides many additional categories you can use to filter web traffic by independent real-world tests.

Highlights

Comprehensive and advanced Web Filtering features Safe Search and user override options. l FortiGuard Web Filtering Services with superior coverage of over 250 million rated websites. l Integration with other FortiOS components, such as User Identification for flexible and secured implementation. l Supports detection for traffic using HTTP protocol (versions 1.0, 1.1, and 2.0).
Ability to configure web filtering by adding URL categories to security policies when operating in flow-based inspection and NGFW policy-based mode. You can set the action to accept or deny to allow or block the applications.

Key features & benefits

Cloud-based Rating Database	Real-time website category rating provides accurate content control.
Wide choice of web filtering technologies	Various web filtering technology options are available to provide each organization the most suitable implementation.
Integrated with other security and networking functions	Allows organizations to simplified networks and reduce TCO.

Features

Cloud-based rating system

Fortinet is a pioneer in cloud-based rating systems for web filtering. FortiOS provides an innovative approach to HTTP and HTTPS web filtering technology by combining the advantages of a cloud-based service offering with layered response caching. The multiple FortiGuard data centers around the world hold the entire categorized URL database and receive rating requests from FortiGate units triggered by browser-based URL requests.

FortiGuard responds to these rating requests with the categories stored for specific URLs, the requesting FortiGate unit then uses its own local profile configuration to determine what action is appropriate to the category, such as: blocking, monitoring, allowing the page, displaying a warning, or requiring authentication to view the page.

Rating responses are also cached directly in FortiGate unit memory so that ratings for frequently used sites can be retrieved directly from the cache, reducing the number of requests to the FortiGuard network. Caching URLs in memory makes URL lookups almost instantaneous while only using a very small amount of system memory.

An appropriately licensed FortiManager appliance can be synchronized to the FortiGuard network and as such can be used in the same way to as the FortiGuard network for managed FortiGate devices. This can further reduce any latency associated with the round trip time for individual rating requests while at the same time ensuring complete database coverage. Consider the combination of a LAN attached FortiGate cluster and FortiManager combination with the potential to handle tens of thousands of requests per second.

Superior coverage

FortiGuard Web Filter ratings are performed by a combination of proprietary methods including text analysis, exploitation of the web structure, and human raters. This service currently rates more than 250 million sites covering billions of URLs with each site able to be rated in multiple categories. The FortiGuard database provides a truly international service with support for 70 languages.

Extensive and flexible categorization

Rated URLs are assigned into one of the 98 categories (including 20 user defined ones) which administrators can then easily manage and control. Administrators can configure and populate local categories or place specific URLs in existing categories should the FortiGuard rating not be in agreement with an organization’s policies and practices.

Rating override

At times, administrators may have to allow approved people to access what they need during periods when an exception to the normal rules is required, while still having enough control that the organization’s web usage policies are not compromised. FortiOS can provide such setup by using alternate profiles.

Protection against malicious URLs

The malicious URL database contains all malicious URLs active in the last month and is organized as one of the categories. With Fortinet Security Fabric, customers can further their protection by having the FortiSandbox add newly discovered URLs to a dynamic URL filter, thus blocking files from being downloaded again from that URL.

Inspection modes

FortiOS web filtering can operate in different modes: proxy-based and flow-based inspection modes and DNS filtering. Each mode has strengths and weaknesses and all three can be active at the same time on different traffic streams.

Proxy-based web filtering uses a proxy to assemble and analyze web content as it passes through the FortiGate unit. If a page is blocked the proxy can replace the blocked page with a customizable web page informing users that the page is blocked. Proxy-based web filtering is the most feature-rich mode, supporting many advanced filters including web content filtering that analyzes web page content according to your custom requirements, Java applet filtering, and blocking invalid URLs.

Flow-based web filtering uses the FortiOS IPS engine to filter web content packets as they pass through the FortiGate unit without any buffering. Flow-based inspection does not use a proxy, so inspected packets are not proxied and altered by the FortiGate unit. Flow-based inspection does not support as many advanced features as proxy-based web filtering.

To control your FortiGate’s security profile inspection mode in FortiOS 5.6, you can select Flow or Proxy Inspection Mode from System > Settings. Having control over flow and proxy mode is helpful if you want to ensure that only flow inspection mode is used.

In most cases proxy mode is preferred because more security profile features are available and more configuration options for these individual features are available. Some implementations, however, may require all security profile scanning to only use flow mode. In this case, you can set your FortiGate to flow mode knowing that proxy mode inspection will not be used. Two new policy modes are available in FortiOS 5.6.

l NGFW mode simplifies applying application control and web filtering to traffic by allowing you to add applications and web filtering profiles directly to policies. This is used in conjunction with flow-based inspection. l Transparent proxy allows you to apply web authentication to HTTP traffic without using the explicit proxy.

DNS web filtering employs DNS lookups to the FortiGuard DNS service to get web page ratings. Filtering is done as part of the DNS lookup and web pages can be blocked or redirected to a web filter block page before the HTTP session starts. As a result, it is lightweight in terms of resource usage although it only supports a limited number of advanced features.

Usage quota

Administrators can set a daily timed access quota by category or category group. Quotas allow access for a specified length of time or traffic volume, calculated separately for each user.

SafeSearch

SafeSearch is a feature of popular search sites that prevents explicit web sites and images from appearing in search results. Although SafeSearch is a useful tool, especially in educational environments, the resourceful user may be able to simply turn it off. Enabling SafeSearch on the FortiGate for the supported search sites can better enforce its use by rewriting the search URL to include the code to indicate the use of the SafeSearch feature.

Restrict YouTube access

In FortiOS 5.6 with inspection mode set to proxy-based, you can set Strict or Moderate access to YouTube in a Web Filter profile.

Manual URL and content filter

FortiOS web filtering offers specific URL filtering by standard, wildcard, and regular expression definition, as well as content filtering by pattern type and language.

Advanced web filter configurations

FortiOS rich feature set includes ability to implement a number of enterprise features such as:

Block HTTP redirects by rating, invalid URLs, HTTP POST actions, and Web resume download l Cookie, Java applet, and ActiveX filter
Rate Images by URL and URLs by domain and IP address

Proxy avoidance preventions

FortiGate is able to improve the effectiveness of the web filtering by preventing users from evading the security implementation. Organizations can use its multiple integrated technologies including proxy site URL, proxy application control, and IPS proxy behavior blocking.

User and device awareness

Most networks in today’s organizations are connected with both corporate and personal mobile devices. User and device awareness provides the option to configure intelligent policies that can effectively enforce security.

To tackle the prevalence of BYOD environments, administrators are able to configure web content access policies with sources defined by IPs, users, and devices, either combined or selectively.

External URL filtering support

In instances where customers have large, existing, deployed implementations of a specific URL filtering solution but replace their legacy firewalls with a FortiGate family, they can still retain their web filtering infrastructure since FortiOS supports both ICAP and WISP.

Monitoring, logging, and reporting

FortiOS empowers an organization to implement security best practices that require continuous monitoring of threats, allowing the organization to adapt to new requirements.

The FortiView dashboards display useful analysis data with detailed and contextual session information, which can be filtered and ranked, with drilldown options also available. This information, including system events activities and administration audit trails, can also be archived via logs.

FortiOS logs all the types of traffic that can connect to or terminate at the FortiGate unit. In turn, these logs can generate useful trending and overview reports.