Alliedassault - Does any1 know how to prevent this?

The thing is...I have a server that I think some1 is crashing...
but not just the game...all the cpu.
Its located at a "server-spot" and Im the only 1 that has a remote to it.(passw. protected..directly & remotely)
Its 1800xp, 1000 ddr 333, 100 mb netcard on 100 mb connection
It runs fine for 1/2 to 1 & 1/2 day then something happens,
seems like it depends on when he spots the server online again...
and it has been happening to many times in a row the past week...
and I have a small clue who could be doing it...
the cpu goes from running awsome to running like its 5 mhz with 1/2 mb memory oOo:
But its still running and it takes me about 5 min. to connect to it by remote (if I make it that is)...
and when im finally in...the game is still on and I cant do anything in it cuz its sooooo slow..not even the rigthclick-menu.
I thougth maybe it was overheating...but its not.(40° at most..has 3 fans)
Then I put a new hdd and put everything up again...same problem.
Then I took it home and its been running for over a week just beautiful
with MOH,COD,TS and more programs but not connected to internet.
I cant find anything rong with it....
My question is:
Does any1 know how to prevent some1 from crashing a cpu or...
somehow see ip# of the one who is doing it...if thats the case?
Or any idea...that it could be somthing alse?

Thank you for your time... beer: