Okay, this is a aggression module. I wrote it, had some issue's with it, and removed it from my mud. I do not garuntee that it will function well without some minor changes.
What this does, is a complete replacement of the aggr_update function you see in update.c, this makes it so that aggression is relative to movement, ie, moving room-to-room causes aggro.
My goal was to allow for monster-on-monster, player-on-monster combat styles. Without bogging the system down too much.
I noticed a large drop in CPU when I put this in, there is also a aggro_update function, which I called every 5 minutes from my event driver. This allows for that little extra if there isn't much in the way of movement going on from the players.
A note: This was once again, written for my mud, at work, and emailed to myself, so you'll have to modify it to bring it up-to-date with your systems requirements, aswell as potentially debugging it. However, it was a very nice addition to CombatMud. So it might be a nice addition to another mud.