ICMP Redirects are used to send routing information to other hosts. As a host itself does not act as a router (in a host only configuration), there is no need to send redirects. Rationale: An attacker could use a compromised host to send invalid ICMP redirects to other router devices in an attempt to corrupt routing and have users access a system set up by the attacker as opposed to a valid system. Fix: Set the net.ipv4.conf.all.send_redirects and net.ipv4.conf.default.send_redirects parameters to 0 in /etc/sysctl.conf and run sysctl -p command: net.ipv4.conf.all.send_redirects=0net.ipv4.conf.default.send_redirects=0 Modify active kernel parameters to match: # /sbin/sysctl -w net.ipv4.conf.all.send_redirects=0 # /sbin/sysctl -w net.ipv4.conf.default.send_redirects=0 # /sbin/sysctl -w net.ipv4.route.flush=1

[no/yes, no/yes]

Set the net.ipv4.conf.all.send_redirects and net.ipv4.conf.default.send_redirects parameters to 0 in /etc/sysctl.conf: net.ipv4.conf.all.send_redirects=0 net.ipv4.conf.default.send_redirects=0 Modify active kernel parameters to match: # /sbin/sysctl -w net.ipv4.conf.all.send_redirects=0 # /sbin/sysctl -w net.ipv4.conf.default.send_redirects=0 # /sbin/sysctl -w net.ipv4.route.flush=1