The TF2 Server hack was my fault. Logged on with unsecure Certificate(ssh) and had a hackable service running(httpd).
So far i've found out that they tried getting access to neds sourcebans database, but then got blocked by WinFW.
Also I've set the TF2 Server to automatically start and restart whenever the system or the server crashes.
(Windows Server 2008 ftw. Running anything as service, without extra tools.)
Team Fortress 2 Server restored. Continueing happily...
(@Ned: Need new Sourcebans PW asap if possible)