Category Archives: FortiOS 6

Best Practices – Web filtering and Patch Management

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Web filtering

FortiGuard Web Filtering can help stop infections from malware sites and help prevent communication if an infection occurs.

  • 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

Patch management

When vulnerabilities are discovered in software, the software vendors release updates that fix these problems. Keeping your software and operating system up-to-date is a vital step to prevent infection and defend against attacks.

  • Follow the latest advisories and reports on the FortiGuard webpage. l Apply updates to all software as the updates become available.
  • FortiGuard Vulnerability Management can help identify security weaknesses in your network. This subscription service is available through FortiScan and FortiAnalyzer units.
  • Apply firmware updates to your FortiGate unit as they are released.
  • Subscribe to FortiGuard AntiVirus and IPS services, so that AntiVirus and IPS scanning engines are automatically updated when new version are released.

Best Practices – Security Profiles (AV, Web Filtering etc.)

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Security Profiles (AV, Web Filtering etc.)

Infection can come from many sources and have many different effects. Because of this, there is no single means to effectively protect your network. Instead, you can best protect your network with the various UTM tools your FortiGate unit offers.

Firewall

  • Be careful when disabling or deleting firewall settings. Changes that you make to the firewall configuration using the GUI or CLI are saved and activated immediately.
  • Arrange firewall policies in the policy list from more specific to more general. The firewall searches for a matching policy starting from the top of the policy list and working down. For example, a very general policy matches all connection attempts. When you create exceptions to a general policy, you must add them to the policy list above the general policy.
  • Avoid using the All selection for the source and destination addresses. Use addresses or address groups. l If you remove all policies from the firewall, there are no policy matches and all connections are dropped. l If possible, avoid port ranges on services for security reasons.
  • The settings for a firewall policy should be as specific as possible. Do not use 0.0.0.0 as an address. Do not use Any as a service. Use subnets or specific IP addresses for source and destination addresses and use individual services or service groups.
  • Use a 32-bit subnet mask when creating a single host address (for example, 255.255.255.255).
  • Use logging on a policy only when necessary and be aware of the performance impact. For example, you may want to log all dropped connections but can choose to use this sparingly by sampling traffic data rather than have it continually storing log information you may not use.
  • It is possible to use security policies based on ‘any’ interface. However, for better granularity and stricter security, explicit interfaces are recommended.
  • Use the comment field to input management data, for example: who requested the rule, who authorized it, etc.
  • Avoid FQDN addresses if possible, unless they are internal. It can cause a performance impact on DNS queries and security impact from DNS spoofing. l For non vlan interfaces, use zones (even if you have only one single interface for members) to allow:
  • An explicit name of the interface to use in security policies (‘internal’ is more explicit than ‘port10’).
  • A split between the physical port and its function to allow port remapping (for instance moving from a 1G interface to a 10G interface) or to facilitate configuration translation, as performed during hardware upgrades.

Security

  • Use NTP to synchronize time on the FortiGate and the core network systems, such as email servers, web servers, and logging services.
  • Enable log rules to match corporate policy. For example, log administration authentication events and access to systems from untrusted interfaces.
  • Minimize adhoc changes to live systems, if possible, to minimize interruptions to the network. When not possible, create backup configurations and implement sound audit systems using FortiAnalyzer and FortiManager.
  • If you only need to allow access to a system on a specific port, limit the access by creating the strictest rule possible.

Authentication

  • You must add a valid user group to activate the Authentication check box on the firewall policy configuration page.
  • Users can authenticate with the firewall using HTTP or FTP. For users to be able to authenticate, you must add an HTTP or FTP policy that is configured for authentication.

Antivirus

  • 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 you receive antivirus signature updates as soon as they are available.
  • To ensure that all AV push updates occur, ensure you have an AV profile enabled in a security policy.
  • Enable only the protocols you need to scan. If you have antivirus scans occurring on the SMTP server, or use FortiMail, it is redundant to have scanning occur on the FortiGate unit as well.
  • Reduce the maximum file size to be scanned. Viruses usually travel in small files of around 1 to 2 megabytes.
  • Do not quarantine files unless you regularly monitor and review them. This is otherwise a waste of space and impacts performance.
  • Examine antivirus reports and log messages 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.

Antispam

l If possible use, a FortiMail unit. The antispam engines are more robust. l Use fast DNS servers. l Use specific security profiles for the rule that will use antispam. l DNS checks may cause false positive with HELO DNS lookup. l Content analysis (banned words) may impose performance overhead.

Intrusion Prevention System (IPS)

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. Refer to the following list of best practices regarding IPS.

  • 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 IPS signature updates as soon as they are available.
  • 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.
  • Create and use security profiles with specific signatures and anomalies you need per-interface and per-rule.
  • Do not use predefined or generic profiles. While these profiles are convenient to supply immediate protection, you should create profiles to suit your network environment.
  • If you do use the default profiles, reduce the IPS signatures/anomalies enabled in the profile to conserve processing time and memory.
  • If you are going to enable anomalies, make sure you tune thresholds according to your environment.
  • If you need protection, but not audit information, disable the logging option. l Tune the IP-protocol parameter accordingly.

Blocking Skype using CLI options for improved detection

If you want to identify or block Skype sessions, use the following CLI command with your FortiGate’s public IP address to improve detection (FortiOS 4.3.12+ and 5.0.2+):

config ips global set skype-client-public-ipaddr 198.51.100.0,203.0.113.0

end

Note that the above syntax is configured using multiple public IP addresses, where a single public IP address may suffice depending on your network configuration.

Email filter

Best Practices – Policy configuration

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Policy configuration

Configuring the FortiGate unit with an ‘allow all’ traffic policy is very undesirable. While this does greatly simplify the configuration, it is less secure. As a security measure, it is best practice for the policy rulebase to ‘deny’ by default, and not the other way around.

Policy configuration changes

On a heavy-loaded system, plan configuration changes during low usage periods in order to minimize impact on CPU usage and established sessions. In this scenario, it is considered a best practice to de-accelerate the hardware-accelerated sessions.

You can configure de-accelerated behaviour on hardware-accelerated sessions using CLI commands to control how the processor manages policy configuration changes. The following CLI commands are to be used:

config system settings set firewall-session-dirty { check-all | check-new | check-policy-option }

end where you want the following to be true:

check-all CPU flushes all current sessions and re-evaluates them. This is the default option.
check-new CPU keeps existing sessions and applies policy changes to new sessions only. This reduces CPU load and the possibility of packet loss.
check-policy-option Use the option selected in the firewall-session-dirty field of the firewall policy (check-all or check-new, as above, but per policy).

Policy whitelisting

  • Allow only the necessary inbound and outbound traffic.
  • If possible, limit traffic to specific addresses or subnets. This allows the FortiGate unit to drop traffic to and from unexpected addresses.

IPS and DoS policies

  • 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.
  • 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.
  • DoS attacks are launched against vulnerabilities. Maintain a FortiGuard IPS subscription to ensure your FortiGate unit automatically receives new and updated IPS signatures as they are released.
  • Use and configure DoS policies to appropriate levels based on your network traffic and topology. This will help drop traffic if an abnormal amount is received. The key is to set a good threshold. The threshold defines the maximum Patch management Policy configuration

number of sessions/packets per second of normal traffic. If the threshold is exceeded, the action is triggered. Threshold defaults are general recommendations, but your network may require very different values. One way to find the correct values for your environment is to set the action to Pass and enable logging. Observe the logs and adjust the threshold values until you can determine the value at which normal traffic begins to generate attack reports. Set the threshold above this value with the margin you want. Note that the smaller the margin, the more protected your system will be from DoS attacks, but your system will also be more likely to generate false alarms.

Email filter

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Email filter

Spam is a common means by which attacks are delivered. Users often open email attachments they should not, and infect their own machine.

l Enable email filtering at the network edge for all types of email traffic. l Use FortiClient endpoint IPS scanning for protection against threats that get into your network. l Subscribe to the FortiGuard AntiSpam Service.

amURL filtering

Best practices for URL filtering can be divided into four categories: flow-based versus proxy based filtering; local category/rating feature; URL filter ‘Exempt’ action; and Deep Scan.

Flow-based versus proxy-based

Try to avoid mixing flow-based and proxy-based features in the same profile if you are not using IPS or Application Control.

Local category/rating feature

Local categories and local rating features consume a large amount of CPU resources, so use these features as little as possible. It is better to use Local categories instead of using the ‘override’ feature, since the ‘override’ feature is more complicated and more difficult to troubleshoot.

URL filter ‘Exempt’ action

When using the URL filter ‘Exempt’ option,webfilter, antivirus and dlp scans are bypassed by default, so use this option only for trusted sites.

Configuration notes: You need to configure ‘Exempt’ actions in the URL filter if you want to bypass the FortiGuard Web Filter.You can configure which particular inspection(s) you want to bypass using the set exempt command in config webfilter urlfilter.

Deep Scan

The ‘Deep Scan’ feature is much heavier on resources than ‘HTTPS URL Scan Only’. Deep Scan is much more accurate, since many sites (such as various Google applications) cannot be scanned separately without deep scanning enabled.

Note: If you configure Deep Scan in the SSL profile and then configure ‘Enable HTTPS URL Scan Only’ in the web filter profile, then Deep Scan is not performed.

Best Practices – Backing up a configuration file using SCP

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Backing up a configuration file using SCP

You can use secure copy protocol (SCP) to download the configuration file from the FortiGate unit as an alternative method of backing up the configuration file or an individual VDOM configuration file. This is done by enabling SCP for and administrator account and enabling SSH on a port used by the SCP client application to connect to the FortiGate unit. SCP is enabled using the CLI commands:

config system global set admin-scp enable

end

Use the same commands to backup a VDOM configuration by first entering the commands:

config global set admin-scp enable end

Best Practices – Performing a configuration backup

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Performing a configuration backup

Once you configure the FortiGate unit and it is working correctly, it is extremely important that you backup the configuration. In some cases, you may need to reset the FortiGate unit to factory defaults or perform a TFTP upload of the firmware, which will erase the existing configuration. In these instances, the configuration on the device will have to be recreated, unless a backup can be used to restore it.

It is also recommended that once any further changes are made that you backup the configuration immediately, to ensure you have the most current configuration available. Also, ensure you backup the configuration before upgrading the FortiGate unit’s firmware. Should anything happen during the upgrade that changes the configuration, you can easily restore the saved configuration.

Always backup the configuration and store it on the management computer or off-site. You have the option to save the configuration file to various locations including the local PC, USB key, FTP and TFTP site.The latter two are configurable through the CLI only.

If you have VDOMs, you can back up the configuration of the entire FortiGate unit or only a specific VDOM. Note that if you are using FortiManager or FortiCloud, full backups are performed and the option to backup individual VDOMs will not appear.

To back up the FortiGate configuration – web-based manager:

  1. Go to Dashboard.
  2. On the System Information widget, select Backup next to System Configuration.
  3. Select to backup to your Local PC or to a USB Disk.

The USB Disk option will be grayed out if no USB drive is inserted in the USB port. You can also backup to the FortiManager using the CLI.

  1. If VDOMs are enabled, select to backup the entire FortiGate configuration (Full Config) or only a specific VDOM configuration (VDOM Config).
  2. If backing up a VDOM configuration, select the VDOM name from the list.
  3. Select Encrypt configuration file.

Encryption must be enabled on the backup file to back up VPN certificates.

  1. Enter a password and enter it again to confirm it. You will need this password to restore the file.
  2. Select Backup.
  3. The web browser will prompt you for a location to save the configuration file. The configuration file will have a .conf extension.

To back up the FortiGate configuration – CLI:

execute backup config management-station <comment>

… or …

execute backup config usb <backup_filename> [<backup_password>]

… or for FTP (note that port number, username are optional depending on the FTP site)…

execute backup config ftp <backup_filename> <ftp_server> [<port>] [<user_name>] [<password>]

… or for TFTP … execute backup config tftp <backup_filename> <tftp_servers> <password>

Use the same commands to backup a VDOM configuration by first entering the commands:

config vdom edit <vdom_name>

Best Practices – Performing a firmware downgrade

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Performing a firmware downgrade

Just like upgrading, you need to make sure it’s done properly. While similar, the steps are somewhat different since there are other pitfalls in this case.

  1. Locate pre-upgrade configuration file.

Step 1 is very important. This is why, when you upgrade you make a backup of your old configuration and save it.

If you don’t, then you’ll need to rebuild manually.

  1. Have copy of old firmware available.

Step 2 is fairly obvious. Even with devices that have multiple partitions and your downgrade process is simply going to be to switch the active partition, this could go wrong. In which case, you may be without Internet access. A professional has a plan for when things go wrong.

  1. Have disaster recovery option on standby — especially if remote.

Step 3 is no different from before. Hopefully you don’t need to format the unit, but be prepared for that, just in case.

  1. Read the release notes — is a downgrade possible, or necessary?

Step 4, once again, is to READ THE RELEASE NOTES. In this case, you will need to do this for the version you are on, and the version you are downgrading too, and everything in between (if you are going back multiple major releases or patches). Maybe the OS switched from 32 to 64 bits somewhere between the two firmware releases. In order to make sure you don’t get nailed by something like that you need to check the upgrade and downgrade information in every major release and patch, as it may have a direct impact on your options.

  1. Double check everything.
  2. Downgrade — all settings, except those needed for access, are lost.

Step 5 and 6 are the same as before. Double check everything, then downgrade.

  1. Restore pre-upgrade configuration.

Step 7 is new. Obviously most settings are lost when you downgrade so in order to get back up and running you will need to restore your old configuration file.

Best Practices – Performing a Firewall Upgrade

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Performing a firmware upgrade

Upgrading a firewall is something that should be compared to upgrading the operating system on your computer. It’s not to be taken lightly! You want to make sure everything is backed up and you have some options available if things go awry. Assuming it all seems to work you also want a list of things to do in order to confirm everything is working properly. Finally, you need enough time to do it. All really simple stuff, but what does this mean in relation to upgrading your FortiGate? It means, you follow these simple steps:

  1. Backup and store old configuration (full configuration backup from CLI).

Digging into this a little, step 1 is easy to understand. Do a full backup of your old configuration. This is all part of your disaster recovery plan. If the upgrade fails in some way you need to make sure you can get the Firewall back up and running. The best way to do this is to get it back to a state where you know what the behavior was. For more information, refer to “Performing a configuration backup” on page 17.

  1. Have copy of old firmware available.

Step 2, is also part of your disaster recovery. If the upgrade fails you might be able to switch the active partition. But as a Professional, you need to be prepared for the worst case scenario where you can’t do that. Which means you’ll need your old firmware.

  1. Have disaster recovery option on standby — especially if remote.

Step 3, is your plan for what to do in the event of a critical failure. As we’re talking FortiGate this means that your firewall doesn’t come back after the upgrade. What this means is that you need to be able to get to the console port in order to find out why. Maybe it’s DHCP and the IP changed, maybe the OS is corrupt, who knows? Get to the console and find out.

There could be a simple fix. If there’s not, then be prepared for a format and TFTP reload.

  1. Read the release notes, including the upgrade path and bug information.

Step 4, READ THE RELEASE NOTES. They contain all kinds of information, known bugs, fixed bugs even upgrade issues like lost configuration settings. Not all upgrade information is ever contained in any products release notes. That does not mean they are devoid of good/useful information. Read them, digest them, then a few days later read them again.

  1. Double check everything.

Step 5, do a double check of everything. Is your TFTP server working, does your console connection function, is there anything in the release notes that could impact your upgrade procedure, do you have your configuration backed up? Make sure you’ve done everything.

Step 6, do the upgrade. Doing an upgrade doesn’t take very long, a few minutes (less a lot of times) but make sure you schedule enough time for it. At the end of the day an upgrade can succeed or fail. If it succeeds you want some time to check/confirm that any important features you have are working (VPNs etc). If it fails you’ll need time to sort things out.