OneTwenty web services temporarily down (attempted hack?)

OneTwenty web services were temporarily down earlier today, possibly due to an attempted hack. The kernel caught a TCP window shrink attempt:

TCP: Treason uncloaked! Peer shrinks window

This page has a few explainations of what the problem could be. The http site at the IP address in question looks to be a vanilla Mandrake install. Running a reverse DNS lookup reveals that the computer is somewhere in China (that is, if it isn’t a masqueraded IP).

Anyhow, the kernel caught the problem and I used iptables to automatically drop packets originating from that IP address. Anyone else have something like this happen recently?

Update: Installed OSSEC per Steve‘s suggestion. The latest version (0.9.3) installs easily (following the instructions in the manual) and even creates the /etc/init.d/ossec file for easy use in Ubuntu!