final guid (as seen by B3) = player qkey | server IP | server port
some hacks auto change players guid to evade bans
some players delete their qkey file to evade bans
B3 bans by guid for UrT. There are plugins that also generate a ip banlist if I'm not mistaken (cannot remember which one)
Here you can see all UrT servers using B3 and the plugins they are using. That can be a good way to discover interesting plugins.