Alias Exploits

As some of you may be aware of, there are some alias exploits in Garry’s Mod to spam the server, causing it to time out.

Example of shit beeing spammed:

I dó got the npc_thinknow Convar fixed, but i have no idea what this possibly could be.
It has something to do with entities, since it also happenend on my other server.
Any help on howto block these exploits would be appreciated.

It’s groundlist.

Thanks mate!