The SUSE operating system must prevent Internet Protocol version 4 (IPv4) Internet Control Message Protocol (ICMP) redirect messages from being accepted.

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.

Verify the SUSE operating system does not accept ICMP redirect messages.

Check the value of the "net.ipv4.conf.all.accept_redirects" variable with the following command:

# sysctl net.ipv4.conf.all.accept_redirects net.ipv4.conf.all.accept_redirects =0

If the returned line does not have a value of "0" this is a finding.

Configure the SUSE operating system to the required kernel parameter by adding the following line to "/etc/sysctl.conf" (or modify the line to have the required value):

net.ipv4.conf.all.accept_redirects =0

Run the following command to apply this value:

# sysctl --system