Information
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 and net.ipv4.conf.default.secure_redirects to 0 protects the system from routing table updates by possibly compromised known gateways.
Solution
Set the following parameters in /etc/sysctl.conf or a /etc/sysctl.d/* file:
Example:
# printf "
net.ipv4.conf.all.secure_redirects = 0
net.ipv4.conf.default.secure_redirects = 0
" >> /etc/sysctl.d/60-netipv4_sysctl.conf
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
}