Enable Antispoofing With Iptables

for i in /proc/sys/net/ipv4/*/rp_filter; do
echo 1 > $f
done

Or simply

echo 1 > /proc/sys/net/ipv4/*/rp_filter (depends on your shell)

This compares the source adress against the routing table

More info about the ~50 options you can find at /usr/src/linux/Documentation/networking/ip-sysctl.txt

~ by princ3 on October 1, 2007.