Hi there.
I just installed Linux on my laptop, and I am quite satisfied with how secure I managed to get it, except for one thing:
The laptop can still accept pings. I would really like to be able to keep someone from pinging the computer.
Does anyone have any idea how to do this?

Thanks in advance,
oostevo

I'm in recycle mode, so check our forum:
here,
here,
and here. If it's iptables you want check out the guruz site mentioned in one of the posts. Even if the syntax differs, the basics remain the same tho.

This command will block all echo-requests
echo "1" > /proc/sys/net/ipv4/icmp_echo_ignore_all

ICMP Broadcasting protection
echo "1" > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts

ICMP Dead Error Messages protection
echo "1" > /proc/sys/net/ipv4/icmp_ignore_bogus_error_responses

Hope this helps

Set up iptables (or whatever firewall) to deny icmp packets. from the outside.
eg. iptables -A INPUT -p icmp DROP .....(or reject)

Mind you pings aren't such a big deal most of the time unless you're going to receive a lot this type of traffic.

Well, I realise that in most cases it is unnecessary to deny ICMP echos, but I am going to be wargaming with my friends using the laptop, and I don't want them to do something stupid like ping flood me.

Thanks for the information - it worked great(ly).

This will log ICMP flooding

$IPTABLES -A INPUT -i $EXT_IF -p icmp --icmp-type echo-request -m limit --limit 12/hour --limit-burst 1 -j LOG --log-level $LOGLEVEL --log-prefix "ICMP flood: "

loging SYN flooding

$IPTABLES -A INPUT -i $EXT_IF -p tcp --syn -m limit --limit 12/hour --limit-burst 1 -j LOG --log-level $LOGLEVEL --log-prefix "SYN flood (Nmap SYN Scan?): "

where $LOGLEVEL=info
$IPTABLES=/sbin/iptables (in my case)
$EXT_IF=external_intrface (in my case ppp0)

For the above to work you need CONFIG_IP_NF_MATCH_LIMIT compiled as module in your kernel

Make life easy, just use Firestarter and under advanced setup theres a option for icmp pings plus you can still ping out.

__________________________________
don't make me go back