I think blocking will not work, the cheater then uses a different userid/team/IP.
I told rebirther already a year back that there workunits are much to small. At this time they were running on my laptop only 7 minutes. They should increase the runtime drastically. This much better for the server.
For counterstrike the cheating I would store all results in a database and if a result is returned a second time, twice of the credit which would be granted will be reduced and the account will be blocked.
Don't know how simple it is to implement it.