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.