Why does the ISDB block layers 3 and 4 of the OSI model when applying...

The Internet Service Database (ISDB) in FortiGate is used to enforce content filtering at Layer 3 (Network Layer) and Layer 4 (Transport Layer) of the OSI model by identifying applications based on their predefined IP addresses and ports.

FortiGate has a predefined list of all IPs and ports for specific applications downloaded from FortiGuard:

● FortiGate retrieves and updates a predefined list of IPs and ports for different internet services from FortiGuard.

● This allows FortiGate to block specific services at Layer 3 and Layer 4 without requiring deep packet inspection.

The ISDB blocks the IP addresses and ports of an application predefined by FortiGuard:

● ISDB works by matching traffic to known IP addresses and ports of categorized services.

● When an application or service is blocked, FortiGate prevents communication by denying traffic based on its destination IP and port number.