What ports it running on, firewall it off.
Or...
It could be your ISP's proxy (my ISP has one) and if your ISP are morons, then they might have made it open. In this case, abuse your ISP on an hourly basis, and trust me it works, its why my dialup connection now drops out every 5 hours, and I get 10kbps on it (which is really good for dialup).