NIMDA

Hi all! I have a Problem with the Iptabels Firewall. The Nimda-Worm has infected our NT Servers and I tried to block the Worm with our iptables Firewall. IPTABLES -I INPUT -p tcp --dport 80 -m string --string cmd.exe -m state --state ESTABLISHED -j REJECT --reject-with tcp-reset But I get this message: Couldn´t load match string:/usr/lib/iptables/libipt_string.so What could I do? Armin