Category Archives: FortiOS 5.4 Handbook

The complete handbook for FortiOS 5.4

Fixed Port

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Fixed Port

Some network configurations do not operate correctly if a NAT policy translates the source port of packets used by the connection. NAT translates source ports to keep track of connections for a particular service.

From the CLI you can enable fixedport when configuring a security policy for NAT policies to prevent source port translation.

config firewall policy edit <policy-id>

…

set fixedport enable

… end

However, enabling fixedport means that only one connection can be supported through the firewall for this

service. To be able to support multiple connections, add an IP pool, and then select Dynamic IP pool in the policy. The firewall randomly selects an IP address from the IP pool and assigns it to each connection. In this case, the number of connections that the firewall can support is limited by the number of IP addresses in the

Accept Policies

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Accept Policies

Accept security policies accept traffic that is coming into the network. These policies allow traffic through the FortiGate unit, where the packets are scanned, translated if NAT is enabled, and then sent out to its destination.

Accept security policies are the most common security policies that are created in FortiOS. These security policies are basic policies, such as allowing Internet access, as well as complex policies, such as IPsec VPN.

Deny Policies

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Deny Policies

Deny security policies deny traffic that is coming into the network. The FortiGate unit automatically blocks traffic that is associated with a deny security policy.

Deny security policies are usually configured when you need to restrict specific traffic, for example, SSH traffic. Deny security policies can also help when you want to block a service, such as DNS, but allow a specific DNS server.

Security Policy 0

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Security Policy 0

 

Any security policy that is automatically added by the FortiGate unit has a policy ID number of zero (0). The most common reasons the FortiGate unit creates this policy is:

  • The IPsec policy for FortiAnalyzer (and FortiManager version 3.0) is automatically added when an IPsec connection to the FortiAnalyzer unit or FortiManager is enabled.
  • The policy to allow FortiGuard servers to be automatically added has a policy ID number of zero.
  • The (default) drop rule that is the last rule in the policy and that is automatically added has a policy ID number of zero.
  • When a network zone is defined within a VDOM, the intra-zone traffic set to allow or block is managed by policy 0 if it is not processed by a configured security policy.

 

This policy can appear in logs but will never appear in the security policy list, and therefore, can never be repositioned in the list.

When viewing the FortiGate firewall logs, you may find a log field entry indicating policyid=0. The following log message example indicates the log field policyid=0 in bold.

2008-10-06 00:13:49 log_id=0022013001 type=traffic subtype=violation pri=warning vd=root SN=179089 duration=0 user=N/A group=N/A rule=0 policyid=0 proto=17 service=137/udp app_type=N/A status=deny src=10.181.77.73 srcname=10.181.77.73 dst=10.128.1.161 dstname=10.128.1.161 src_int=N/A dst_int=”Internal” sent=0 rcvd=0 src_port=137 dst_port=137 vpn=N/A tran_ip=0.0.0.0 tran_port=0

Local-In Policies

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Local–In Policies

On the FortiGate unit, there are a number of protocols and traffic that is specific to the internal workings of FortiOS. For many of these traffic sources, you can identify a specific port/IP address for this self-originating traffic. The following traffic can be configured to a specific port/IP address:

  • SNMP
  • Syslog
  • alert email
  • FortiManager connection IP
  • FortiGuard services
  • FortiAnalyzer logging
  • NTP
  • DNS
  • Authorization requests such as RADIUS
  • FSSO

 

Security policies control the flow of traffic through the FortiGate unit. The FortiGate unit also includes the option of controlling internal traffic, that is, management traffic.

Each interface includes an allow access configuration to allow management access for specific protocols. Local policies are set up automatically to allow all users all access. Local-in policies takes this a step further, to enable or restrict the user with that access. This also extends beyond the allow access selection.

Local-in policies are configured in the CLI with the commands:

 

config firewall local-in-policy edit <policy_number>

set intf <source_interface>

set srcaddr <source_address>

set dstaddr <destination_address>

set action {accept | deny} set service <service name> set schedule <schedule_name>

end

For example, you can configure a local-in policy so that only administrators can access the FortiGate unit on weekends from a specific management computer at 192.168.21.12, represented by the address object mgmt- comp1, using SSH on port 3 (192.168.21.77 represented by the address object FG-port3) using the Weekend schedule which defines the time the of access.

 

config firewall local-in-policy edit <1>

set intf port3

set srcaddr mgmt-comp1 set dstaddr FG-port3 set action accept

set service SSH

set schedule Weekend end

You can also disable a policy should there be a requirement to turn off a policy for troubleshooting or other purpose. To disable a policy enter the commands:

 

config firewall local-in-policy edit <policy_number>

set status disable end

Use the same commands with a status of enable to use the policy again. Local-in policies are also supported for IPv6 by entering the command

config firewall local-in-policy6.

DoS Protection

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DoS Protection

Denial of Service (DoS) policies are primarily used to apply DoS anomaly checks to network traffic based on the FortiGate interface it is entering as well as the source and destination addresses. DoS checks are a traffic anomaly detection feature to identify network traffic that does not fit known or common traffic patterns and behavior. A common example of anomalous traffic is the denial of service attack. A denial of service occurs when an attacking system starts an abnormally large number of sessions with a target system. The large number of sessions slows down or disables the target system, so that legitimate users can no longer use it.

DoS policies are similar to firewall policies except that instead of defining the way traffic is allowed to flow, they keep track of certain traffic patterns and attributes and will stop traffic displaying those attributes. Further, DoS policies affect only incoming traffic on a single interface. You can further limit a DoS policy by source address, destination address, and service.

DoS configurations have been changed a couple of times in the past. In FortiOS 4.0, DoS protection is moved to the interface policy, so when it is enabled, it is the first thing checked when a packet enters FortiGate. Because of this early detection, DoS policies are a very efficient defence that uses few resources. Denial of service attacks, for example, are detected and its packets dropped before requiring security policy look-ups, antivirus scans, and other protective but resource-intensive operations.

A DoS policy examines network traffic arriving at an interface for anomalous patterns usually indicating an attack. This does not mean that all anomalies experience by the firewall are the result of an intentional attack.

Because an improperly configured DoS anomaly check can interfere with network traffic, no DoS checks are preconfigured on a factory default FortiGate unit. You must create your own before they will take effect. Thresholds for newly created sensors are preset with recommended values that you can adjust to meet the needs of your network.

To create a Denial of Service policy determine if it needs to be an IPv4 or IPv6 policy, then goto:

Policy & Objects > Policy > DoS Policy for IPv4.

Policy & Objects > Policy > IPv6 DoS Policy for IPv6.

The Enable SSH Deep Scan feature is enabled by default when creating a new SSL/SSH Inspection profile. There are situations were this feature can cause issues so be sure that you would like it enabled before applying it.

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VPN Policies

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VPN Policies

At one point, if you wanted to have secure digital communications between 2 points a private network would be created. This network would only allow the people that were intended to get the communications on it. This is very straightforward if the 2 points are in the same room or even in the same building. It can all be done physically. If you are supposed to be on the secure network VPNs are an answer to one of today’s biggest concerns, how to make digital communications secure between to points that must communicate over the Internet which anybody can have access to

 

IPsec Policies

IPsec policies allow IPsec VPN traffic access to the internal network from a remote location. These policies include authentication information that authenticates users and user group or groups. These policies specify the following:

  • the FortiGate firewall interface that provides the physical connection to the remote VPN gateway, usually an interface connected to the Internet
  • the FortiGate firewall interface that connects to the private network
  • IP addresses associated with data that has to be encrypted and decrypted
  • optional: a schedule that restricts when the VPN can operate, and services (or types of data) that can be sent.

For a route-based (interface mode) VPN, you do not configure an IPsec security policy. Instead, you configure two regular ACCEPT security policies, one for each direction of communication, with the IPsec virtual interface as the source or destination interface, as appropriate.

Security profiles

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Security profiles

Where security policies provide the instructions to the FortiGate unit for controlling what traffic is allowed through the device, the Security profiles provide the screening that filters the content coming and going on the network. Security profiles enable you to instruct the FortiGate unit about what to look for in the traffic that you don’t want, or want to monitor, as it passes through the device.

A security profile is a group of options and filters that you can apply to one or more firewall policies. Security profiles can be used by more than one security policy. You can configure sets of security profiles for the traffic types handled by a set of security policies that require identical protection levels and types, rather than repeatedly configuring those same security profile settings for each individual security policy.

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

Security profiles are available for various unwanted traffic and network threats. Each are configured separately and can be used in different groupings as needed. You configure security profiles in the Security Profiles menu and applied when creating a security policy by selecting the security profile type.

There is a separate handbook for the topic of the Security Profiles, but because the Security Profiles are applied through the Firewall policies it makes sense to have at least a basic idea of what the security profile do and how they integrate into the FortiGate’s firewall policies. The following is a listing and a brief description of what the security profiles offer by way of functionality and how they can be configured into the firewall policies.

 

AntiVirus

Antivirus is used as a catch all term to describe the technology for protection against the transmission of malicious computer code sometimes referred to as malware. As anyone who has listened to the media has heard that the Internet can be a dangerous place filled with malware of various flavours. Currently, the malware that is most common in the Internet, in descending order, is Trojan horses, viruses, worms, adware, back door exploits, spyware and other variations. In recent years, not only has the volume of malicious software become greater than would have been believed when it first appeared but the level of sophistication has risen as well.

The Antivirus Filter works by inspecting the traffic that is about to be transmitted through the FortiGate. To increase the efficiency of effort it only inspects the traffic being transmitted via the protocols that it has been configured to check. Before the data moves across the FortiGate firewall from one interface to another it is checked for attributes or signatures that have been known to be associated with malware. If malware is detected, it is removed.

 

Web Filtering

Malicious code is not the only thing to be wary of on the Internet. There is also the actual content. While the content will not damage or steal information from your computer there is still a number of reasons that would require protection from it.

In a setting where there are children or other sensitive people using the access provided by a connected computer there is a need to make sure that images or information that is not appropriate is not inadvertently displayed to them. Even if there is supervision, in the time it takes to recognize something that is inappropriate and then properly react can expose those we wish to protect. It is more efficient to make sure that the content cannot reach the screen in the first place.

In an organizational setting, there is still the expectation that organization will do what it can to prevent inappropriate content from getting onto the computer screens and thus provoking an Human Resources incident. There is also the potential loss of productivity that can take place if people have unfiltered access to the Internet. Some organizations prefer to limit the amount of distractions available to tempt their workers away from their duties.

The Web filter works primarily by looking at the destination location request for a HTTP(S) request made by the sending computer. If the URL is on a list that you have configured to list unwanted sites, the connection will be disallowed. If the site is part of a category of sites that you have configured to deny connections to the session will also be denied. You can also configure the content filter to check for specific key strings of data on the actual web site and if any of those strings of data appear the connection will not be allowed.

 

Application Control

Application Control is designed to allow you to determine what applications are operating on your network and to the also filter the use of these applications as required. Application control is also for outgoing traffic to prevent the use of applications that are against an organization’s policy from crossing the network gateway to other networks. An example of this would be the use of proxy servers to circumvent the restrictions put in place using the Web Filtering.

 

Intrusion Protection (IPS)

Intrusion Prevention System is almost self explanatory. In the same way that there is malware out on the Internet that the network needs to be protected from there are also people out there that take a more targeted approach to malicious cyber activity. No operating system is perfect and new vulnerabilities are being discovered all of the time. An intrusion prevention system is designed to look for activity or behavior that is consistent with attacks against your network. When attack like behavior is detected it can either be dropped or just monitored depending on the approach that you would like to take.

As new vulnerabilities are discovered they can be added to the IPS database so that the protection is current.

 

Email Filtering

Spam or unsolicited bulk email is said to account for approximately 90% of the email traffic on the Internet. Sorting through it is both time consuming and frustrating. By putting an email filter on policies that handle email traffic, the amount of spam that users have to deal with can be greatly reduced.

 

Data Leak Prevention (DLP)

Data Leak Prevention is used to prevent sensitive information from leaving your network. When people think of security in the cyber-world one of the most common images is that of a hacker penetrating your network and making off with your sensitive information, but the other way that you can lose sensitive data is if someone already on the inside of your network sends it out. This does not have to be an act of industrial espionage. It can just be a case of not knowing the policies of the organization or a lack of knowledge of security or laws concerning privacy.

For instance, a company may have a policy that they will not reveal anyone’s Social Security number, but an employee emails a number of documents to another company that included a lengthy document that has a Social Security number buried deep within it. There is not malicious intent but if the information got out there could be repercussions.

If an organization has any information in a digital format that it cannot afford for financial or legal reasons, to leave its network, it makes sense to have Data Leak Prevention in place as an additional layer of protection.

 

VoIP

Voice over IP is essentially the protocols for transmitting voice or other multimedia communications over Internet Protocol networks such as the Internet. The Security Profiles VoIP options apply the SIP Application Level Gateway (ALG) to support SIP through the FortiGate unit. The SIP ALG can also be used to protect networks from SIP-based attacks.

 

ICAP

Internet Content Adaptation Protocol (ICAP) off loads HTTP traffic to another location for specialized processing. The purpose of this module when triggered is to send the incoming HTTP traffic over to a remote server to be processed thus taking some of the strain off of the resources of the FortiGate unit. The reasons for the specialized process could be anything from more sophisticated Antivirus to manipulation of the HTTP headers and URLs.

 

EndPoint Control

EndPoint Control makes sure that certain standards are kept. When a computer on the Internet becomes connected to the FortiGate unit by VPN that computer is now part of the same network and therefore needs to be subject to the same levels of protection, not only to protect the computer but the network. In the EndPoint Control section you can set the minimum standards for things like AntiVirus software and VPN software.

 

Proxy Option Components

Any time a security profile that requires the use of a proxy is enabled the Proxy Options field will be displayed. Certain inspections defined in security profiles require that the traffic be held in proxy while the inspection is carried out and so the Proxy Options are there to define the parameters of how the traffic will be processed and to what level the traffic will be processed. In the same way that there can be multiple security profiles of a single type there can also be a number of unique Proxy Option profiles so that as the requirements for a policy differ from one policy to the next you can also configure a different Proxy Option profile for each individual policy or you can use one profile repeatedly.

The Proxy Options refer to the handling of the following protocols:

  • HTTP l  SMTP l  POP3 l  IMAP
  • FTP
  • NNTP
  • MAPI
  • DNS
  • IM

 

The configuration for each of these protocols is handled separately.

It should also be noted that these configurations apply to only the Security Profiles Proxy-based processes and not the Flow-based processes.

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