Strange L4D2 glitch/hack/exploit

[Mac2]

At first I thought my mouse was playing up as occaisionally my mouse would jerk off what i was aiming at as if my sensitivity shot and and I nudged the mouse.

It became obvious that this was intentional last night. Who ever is doing this got a bit carried away. This behaviour never happened when the game was quiet it only occurred when I was aiming at something important. Sometimes I could hear a windows "bing bong" noise when this happened

It is making the game unplayable. I played on my server this morning fine and I have played on other servers no problem. It only seems to happen when a small group of 4 or 5 regular players are on. Two of these guys have some admin rights as well.

I think it is one of the regulars sadly but does anyone know what might cause this? How do I stopp it and find out who it is ? Or am I mad?

 

[Mac2]

I could get fraps but I might not be able to post something for a day or two. It was so obviously deliberate last night and it only happens when a few players are playing. I think the main supect is on now I will see if anything happens when I join now.

 

[Mac2]

I am now pretty certain its the person who I thought it was. He asked to join a game I was already playing but i said he couldnt except for the other team. He did the mouse trick once randomly. He has removed his tag as well.

I just cant understand hw he does it