I have a problem with certain hackers messing with my router. I want to add a line to IPTABLES that will search all traffic arriving on a certain port for a certain text string in the payload part of the packet - not the header. I am told that I need to add the following line to my IPTABLES: iptables -A INPUT -p UDP --dport 999 -m string --string 'badstring' -j DROP But that produces an error: iptables v1.3.8: Couldn't load match `string':File not found So I'm thinking that the "String" IPTABLES module is not loaded for some reason. So the question is: How do I make this work? Do I need to recompile IPTABLES? Does the Toastman source include the STRING module source? Thanks in advance.