Permaban them, you don't want the same people using up your bandwith.

make sure that the mod has a SDK (software development kit) or their source code, so we can make modifications to that mod (i don't know if there are mods with sdk) and let me know

lackote do you have msn or icq?

remkow i added you in msn

Well I know this isn't the same thing I'm about to tell you but I doubt you will be successful with trying to exploit online games by spiking it's updates. First you would have to find a game which distribute its autoupdates as executable then pwn their update server and change the binary. Most of them simply download it's own package format and extract the files not mentioning that the programmers probably do implement integrity check on the client side.

So there is a site called mmowned where you can buy/sell/trade stolen accounts, what you can also get easily with password stealers if you doing ppi in big... You can sell online mmo accounts as high as 800Euro/1 account depending on the characters. If any of you involved in selling these just drop me a pm, I can provide you with them. Of course you need to be an experienced seller and know a lot about the game, forums, community to sell them, also need good social engineering skills for this.

Take the DLL of a known, open source mod and add you payload downloading dirty code. It shouldn't be hard. If you use the HL1 SDK for instance, you have hl,tf,dmc,etc and on HL2 I'm not sure, I've access to the SDK but never actually messes with it.