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The OS X system must ignore IPv4 ICMP redirect messages.


Overview

Finding ID Version Rule ID IA Controls Severity
V-76135 AOSX-12-001200 SV-90823r1_rule Medium
Description
ICMP redirects are broadcast to reshape network traffic. A malicious user could craft fake redirect packets and try to force all network traffic to pass through a network sniffer. If the system is not configured to ignore these packets, it could be susceptible to this kind of attack.
STIG Date
Apple OS X 10.12 Security Technical Implementation Guide 2018-12-24

Details

Check Text ( C-75821r1_chk )
To check if the system is configured to ignore "ICMP redirect" messages, run the following command:

sysctl net.inet.icmp.drop_redirect

If the value is not "1", this is a finding.
Fix Text (F-82773r1_fix)
To configure the system to ignore "ICMP redirect" messages, add the following line to "/etc/sysctl.conf", creating the file if necessary:

net.inet.icmp.drop_redirect=1