The Palo Alto Networks security platform must block outbound ICMP Destination Unreachable, Redirect, and Address Mask reply messages.

Internet Control Message Protocol (ICMP) messages are used to provide feedback about problems in the network. These messages are sent back to the sender to support diagnostics. However, some messages can also provide host information and network topology that may be exploited by an attacker.

Review the vendor documentation for more information about "How to Allow/Block ICMP Error Reporting Packets".

Note that this setting is only available in the Zone Protection profile option, not in the DoS protection profile. Thus, where IDS is part of the function of Palo Alto, a Zone Protection profile is required to comply with this requirement.

Verify a zone protection profile is configured for each outgoing zone that drops all ICMP Destination Unreachable, Redirect, and Address Mask reply messages.

1. Navigate to the "Zone Protection Profile" configuration screen. 2. Select the "Packet Based Attack Protection" tab. 3. Select the "ICMP Drop" tab.

If the "Discard ICMP embedded with error message" box is not checked for each internal or DMZ zone, this is a finding.

Create a zone protection profile for each outgoing zone that drops any ICMP Destination Unreachable, Redirect, and Address Mask reply messages.

1. Navigate to the "Zone Protection Profile" configuration screen. 2. Select the "Packet Based Attack Protection" tab. 3. Select the "ICMP Drop" tab. 4. Check the "Discard ICMP embedded with error message" box.