The system must not send IPv4 ICMP redirects by default.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-67745	AOSX-11-001210	SV-82235r1_rule		Medium

Description
ICMP redirects are broadcast in order to reshape network traffic. A malicious user could use the system to send fake redirect packets and try to force all network traffic to pass through a network sniffer. Disabling ICMP redirect broadcasts mitigates this risk.

STIG	Date
Apple OS X 10.11 Security Technical Implementation Guide	2018-01-04

Details

Check Text ( C-68311r1_chk )
To check if the system is configured to send "ICMP redirects", run the following command: sysctl net.inet.ip.redirect If the values are not set to "0", this is a finding.

Fix Text (F-73859r1_fix)
To configure the system to not send "ICMP redirects", add the following line to "/etc/sysctl.conf", creating the file if necessary: net.inet.ip.redirect=0