Esempio di utilizzo del firewall iptables per bloccare e loggare le richieste ICMP (es: ping) :
# iptables -A INPUT -p icmp -j LOG --log-level info --log-prefix "ICMP: "
# iptables -A INPUT -p icmp -j DROP
Esempio di log output :
Mar 13 13:55:55 server kernel: ICMP: IN=eth0 OUT= MAC=XX:XX:XX:XX SRC=192.168.0.2 DST=192.168.0.1 LEN=60 TTL=128 ID=23414 PROTO=ICMP TYPE=8
Mar 13 13:56:00 server kernel: ICMP: IN=eth0 OUT= MAC=XX:XX:XX:XX SRC=192.168.0.2 DST=192.168.0.1 LEN=60 TTL=128 ID=23423 PROTO=ICMP TYPE=8
Mar 13 13:56:05 server kernel: ICMP: IN=eth0 OUT= MAC=XX:XX:XX:XX SRC=192.168.0.2 DST=192.168.0.1 LEN=60 TTL=128 ID=23426 PROTO=ICMP TYPE=8