i was on my server yesterday when some guy comes in tell us how he is can wreck us n shit, then he starts saying the our server is going down.  he kept saying shit about my server and hes gonna crash it or something.  so i banned the guy, then no more than 1 minute later pings start shotting sky high and ppl started freezing and dissconnecting.  i even started getting laggy, an im on lan. then i shut the server off and restarted it.  when i joined i noticed that the console didnt show it had added master servers but it still said connected to steam servers.  when i joined it was still really laggy.  i restarted it again and it added the master servers and the no more lag for me but nobody could connect to my server.  i tried a couple things after that but nobody could connect. i realized it must have been a connection problem only cause the server seemed fine no problems.  so i checked my router settings and everything was changed.  all ports where unforwarded, filters where all changed also.  i redid everything and it works fine again.  but who the hell did he do that? im afraid that its gonna happen again though.  i know the guys steam id and his server ip also, so i can probably find him again.