3.2.3 Ensure secure ICMP redirects are not accepted (Scored)

Level 1 - Server
Level 1 - Workstation 

Secure ICMP redirects are the same as ICMP redirects, except they come from gateways listed on the default gateway list. It is assumed that these gateways are known to your system, and that they are likely to be secure.

It is still possible for even known gateways to be compromised. Setting net.ipv4.conf.all.secure_redirects to 0 protects the system from routing table updates by possibly compromised known gateways.

Run the following command and verify output matches:

# sysctl net.ipv4.conf.all.secure_redirects 
net.ipv4.conf.all.secure_redirects = 0 
# sysctl net.ipv4.conf.default.secure_redirects 
net.ipv4.conf.default.secure_redirects = 0

Set the following parameter in the /etc/sysctl.conf file:

net.ipv4.conf.all.secure_redirects = 0 
net.ipv4.conf.default.secure_redirects = 0

Run the following commands to set the active kernel parameters:

# sysctl -w net.ipv4.conf.all.secure_redirects=0 
# sysctl -w net.ipv4.conf.default.secure_redirects=0 
# sysctl -w net.ipv4.route.flush=1