Information
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.
Solution
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