FortiGate Inspection Mode
You can select Flow or Proxy Inspection Mode from the System Information dashboard widget to control your FortiGate's security profile inspection mode. 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).
Switching to Flow Inspection Mode also turns off WAN Optimization, Web Caching, the Explicit Web Proxy, and the Explicit FTP Proxy making sure that no proxying can occur.
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.
If you select 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 Anti-Spam profile to a firewall policy.
Proxy mode is the default inspection mode in FortiOS 5.4.
Changing between proxy and flow mode
Proxy mode is enabled by default and you change to flow mode by changing the Inspection Mode on the System Information dashboard widget.
When you select Flow-based you are reminded that 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.
When 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 Information dashboard widget.
If your FortiGate has multiple VDOMs, you can set the inspection mode independently for each VDOM. Use the top left dropdown menu to go to Global > System > VDOM. Click Edit for the VDOM you wish to change and select the Inspection Mode.
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|
|Cloud Access Security Inspection||x||x|
|Data Leak Protection||x||x|
|Web Application Firewall||x|
|Web Rating Overrides||x||x|
|Web Profile Overrides||x|
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.
In flow mode, antivirus and web filter profiles only include flow-mode features. Web filtering and virus scanning is 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.
|CASI does not work when using proxy-based profiles for AV or Web filtering. Make sure to only use flow-based profiles in combination with CASI on a specific policy.|
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.
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
|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
|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|
|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|
|Block malicious URLs discovered by FortiSandbox||yes||yes|
|Web Content Filter||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|
|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|
|Filter Per-User Black/White List||yes||no|