iptables -t filter -A DROP_TRACE -o eth0 -p udp -m recent --name Drop_Traceroute --update --seconds 200 --rdest -j DROP iptables -t filter -A DROP_TRACE -o eth0 -p udp -m recent --name Drop_Traceroute --set --rdest -m ttl --ttl-eq 1 -j DROP iptables -t filter -A DROP_TRACE -o eth0 -p icmp -m recent --name Drop_Traceroute --update --seconds 200 --rdest -j DROP iptables -t filter -A DROP_TRACE -o eth0 -p icmp -m recent --name Drop_Traceroute --set --rdest -m ttl --ttl-eq 1 -j DROP
The only thing that I have not figured out as of yet how to do is DROP the first packet that the firewall sees as every attempt that I made, even a DROP policy on the FORWARD and OUTPUT chain, did not block the first "TTL Time Exceeded" response.
I just figured it out and have tested it. I *think* the reason that my first script did not work for the first router is b/c the raw routing code will send the ICMP TTL time exceeded message before any of the chains in the filter table have a chance to process the packet. Hens my using the nat:PREROUTING chain. I have also made the filtering process easier too as you do not have to filter in the filter:INPUT and filter:FORWARD chains, just the nat:PREROUTING now.
iptables -t nat -A PREROUTING -i $LAN -p udp -m recent --name Drop_Traceroute --update --seconds 200 --rdest -j DROP iptables -t nat -A PREROUTING -i $LAN -p udp -m recent --name Drop_Traceroute --set --rdest -m ttl --ttl-eq 1 -j DROP iptables -t nat -A PREROUTING -i $LAN -p icmp -m recent --name Drop_Traceroute --update --seconds 200 --rdest -j DROP iptables -t nat -A PREROUTING -i $LAN -p icmp -m recent --name Drop_Traceroute --set --rdest -m ttl --ttl-eq 1 -j DROP
This will prevent any traceroutes via the methods mentioned before from any computer coming in on interface $LAN.
Grant. . . .
