Why does the ISDB block layers 3 and 4 of the OSI model when applying content filtering? (Choose two.)

The Fortinet Internet Service Database (ISDB) is a feature that simplifies firewall policy creation by grouping all IP addresses, protocols, and port numbers associated with a specific internet service (like Microsoft 365 or Google Services). FortiGuard Labs continuously maintains and updates this database, which the FortiGate downloads. When an ISDB object is used in a firewall policy with a 'deny' action, the FortiGate blocks traffic at OSI Layers 3 (IP addresses) and 4 (TCP/UDP ports) that matches the entries in the database for that specific service. This provides an efficient way to control access without manually tracking all of a service's network endpoints.

C. The ISDB is a database of network endpoints, not an inspection mode. It can be used in firewall policies operating in either flow or proxy mode; it is not exclusive to proxy mode.
D. Limiting access by URL and domain is a Layer 7 function performed by the Web Filter security profile, not the ISDB, which operates primarily at Layers 3 and 4.

1. FortiOS 7.4.0 Administration Guide

Page 1010

Section: Internet Service Database.

"The FortiGuard Internet Service Database is a comprehensive

up-to-date list of all public IP addresses used by popular internet services... Each Internet Service can contain multiple entries

and each entry consists of an IP address or range

and a protocol and port number." This statement directly supports options A and B by defining the ISDB as a list of IPs and ports provided by FortiGuard.

2. FortiOS 7.4.0 Administration Guide

Page 1011

Section: Internet Service Database.

"When an Internet Service is selected as the source or destination in a firewall policy

traffic matching any of the IP addresses and port numbers in the service will have the policy's action applied to it." This confirms that the ISDB's mechanism is to match and block (or allow) based on the predefined IP addresses and ports (Layers 3 and 4).

3. FortiOS 7.4.0 Administration Guide

Page 1178

Section: Web filter.

"The web filter security profile can inspect HTTP

HTTPS

and FTP traffic... You can configure the web filter profile to block or allow access to web sites by matching their URLs against lists of URLs..." This clearly distinguishes the function of Web Filtering (URL/domain-based) from the ISDB (IP/port-based)

invalidating option D.