Offloading using ICAP
If you enable ICAP in a security policy, HTTP traffic intercepted by the policy is transferred to an ICAP server in the ICAP profile added to the policy. Responses from the ICAP server are returned to the FortiGate unit which forwards them to an HTTP client or server.
You can offload HTTP responses or HTTP requests (or both) to the same or different ICAP servers.
If the FortiGate unit supports HTTPS inspection, HTTPS traffic intercepted by a policy that includes an ICAP profile is also offloaded to the ICAP server in the same way as HTTP traffic.
When configuring ICAP on the FortiGate unit, you must configure an ICAP profile that contains the ICAP server information; this profile is then applied to a security policy.