Preventing Counter Strike DoS with iptables

Last weeks, the spread of csdos.pl, a perl script that aimed to take down Counter Strike 1.6 server, is on rise. One of my servers is suffered from this attack and force me to take an action to prevent them. The solutions is using iptables with string match support. I found an example of iptables rule on the net, but it doesn’t work for the current version of Linux kernel.
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Iptables 1.3.5 string match support

Untuk menggunakan iptables yang support string match, maka kernel Linux yang dipakai harus support juga. Silakan diperiksa (pada kernel 2.6.23.9) di Networking —> Networking options —> Network packet filtering framework (Netfilter) —> Core Netfilter Configuration —> string match support) atau CONFIG_NETFILTER_XT_MATCH_STRING=y (atau =m jika sebagai modul) di file .config. Download filesnya disini:

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