Ok ... so I will not give clear solution but let me give some tips:
1) First of all this issue is old and known since many years...
Here is first official posted request for help with this kind of attack:
2) TIP: Person who is doing this is originally from China and NO it has no relations with any TQ - he just try to molest your server - soon you should receive some kind of message asking to give money to stop ...
3) Blocking Chinese IPs will help only partially as this person will start using other IPs...
4) How this is being done:
this person MUST create account on your server and login. As being logged to Msg server he will start sending own additional packets to server as he wish... yes he knows how to ...
TIP: If you know how and what to do - simply use packet sniffer and record everything ... and start learning what is happening ...
Solutions?
* for sure ban all China, Korea and similar countried totally!
* start control of registration to your server - email confirmation or even by hand confirmation newly created accounts should help for a while...
* Learn from packets whats he's doing so you will start putting into server blocks to prevent this from happening - if you dont know how to start from no one will help you sorry...
*(added) Blocking proxies and voulnarable IPs under firewalls might help little bit as well (but still not ultimate solution!)
P.S.
You will ask how to know who he is? Well this is easly to know - if you know what you are doing...
Sorry if I didnt give clear solution but these tips should help to start somwhere
Remember - Eveyrthing is possible to stop - just sometimes need time to do this.. If you know how to learn on ongoing problems and can always make solutions - you have nothing to be worry ...
good luck