Quote Originally Posted by Endless
It means they are trying to connect to netbus, whose default port is 12345. Netbus is an old trojan, that as far as I know doesn't self propagate, but rather is injected in normal executables or disguised as one. Any AV should pick netbus, so unless you don't have one, there's nothing to worry about.

Also, I'd like to know where you got the idea it comes from FFChat.
If it's Netbus then it's probably a few script kiddies that have no idea what they're doing.