Server Crasher

Ok so this is the story. I resently banned a faggot on my friend’s server who kept threating me that if I banned him, he will use some server crasher thing on us. He was a 12 year old spoiled brat, so I didn’t believe him. But since then we have been getting random multiple crashes. I think that he may actually posses some sort of Server Crasher. Is there anyway of making this stop?

Block his IP

How do I do that?

addip on srcds, IPSec on Windows, IPTables on Linux.