I have catch DRI Clan stealing guid from players on there server. They used 2 players guid to gain commands on LZ Clan server and use the calls to screw with the server. On top of that there leaders have all been catch hacking
And there server doesnt run punkbuster because they wouldnt be able to log on if they did.
I have also seen them using the info to hack with other guid to give other clan or players a bad name, I would look at the ip to be sure that it is your clan members or not they cant use the same ip. they have also used a log on client with multiple logg in about 20 or 30 a time. This is pretty easy to fix by subnet ban by banning the ip range.
Hope the info will help others.
Happy fraging [LZ]Hammer