AlmaLinux OS 9 must ignore Internet Control Message Protocol (ICMP) redirect messages.
An XCCDF Rule
Description
ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages modify the host's route table and are unauthenticated. An illicit ICMP redirect message could result in a man-in-the-middle attack. This feature of the IP protocol has few legitimate uses. It should be disabled unless absolutely required.
- ID
- SV-269244r1050126_rule
- Version
- ALMA-09-018610
- Severity
- Medium
- References
- Updated
Remediation Templates
A Manual Procedure
Configure AlmaLinux OS 9 to ignore ICMP redirect messages.
Create a numbered *.conf file in /etc/sysctl.d/ with the following content:
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.default.accept_redirects = 0