That sounds like a vulnerability in one of your mods. I won't claim Anti TCC is secure in that regard (those have far more time to find loopholes than I do), but let me put it this way: The 3SPN mod had the biggest exploited security hole in it that I've ever seen, one you could use to take control of the entire server. While it has been rewritten from scratch since then, there's no guarantee they didn't leave another gapping hole like that.
I'm not saying it's TAM, though. It could be any mod on your server. Like Carpe said: If you can't figure it out, at least make sure you keep that per4son out of your server. (Did you piss anyone off or why are you
attracting people like that?)