[therainycat]

If you know who's that guy, log events he's pushing to your server (in callbacks, such as OnPlayerGiveDamage etc.) and log how his data changes by time (in OnPlayerUpdate). If you know exactly, which player does harm, log only his data (i suggest to write that log to separate file).

Here's example of data logging (I wrote it as "sandbox" gamemode for testing new cheats and crashers).
http://pastebin.com/QHf1wg5g