Hack / TeamSpeak Bug?

[Vardy]

I was on my TS earlier when some guy kept joining and leaving as Guest*. i tried banning his IP but it never showed in the IP bans. i used the webadmin interface to add a pass to the server and i thought everything was fixed. but however he was still on the teamspeak but was 'invisible' to everybody. he sent me priv messages saying "you cant ban what you cant see".
at the same time as all this there was another guy on the TS aswell who was also unknown to me. he aswell didnt have a mic and was also sending me messages.
i eventually stopped the server and contacted my host. before i started the server again i made sure that they didnt register and my server had a decent password.

i was just wondering if the invisible person was a hack or an expliot/bug in the TS.
the current version of the teamspeak is 2.0.20.1 im not sure if i am able to update it to a beta because its not hosted by me. is ther anyway to prevent this happening again?
are there any programs that ban people if they connect so many times in a given amount of time? or log the connections so i can view them after?

[BHKai]

You will have to talk to your host, you can log using the TS server, and access the logs with telnet. You will have to get the server updated if you do not want people to use those hacks that have been developed.