How protocol requests are managed

When a protocol request is made, the following steps are used to determine whether to block or permit the request:

1. Determine the protocol (or Internet application) name.
2. Identify the protocol based on the request destination address.
3. Search for related port numbers or IP addresses in custom protocol definitions.
4. Search for related port numbers, IP addresses, or signatures in pre-defined protocol definitions.

If any of this information cannot be determined, all content associated with the protocol is permitted.

If the protocol is FTP, HTTPS, or gopher, a check is first performed to see if the protocol is blocked. If the protocol is permitted, Filtering Service performs a URL lookup to see if the requested site is permitted or blocked.