Let's see:
Shields UP!
https://grc.com/x/ne.dll?bh0bkyd2 A great way to test open "back doors" on your computer through your internet connection's IP address. Click on both the "Test My Shields!" and "Probe My Ports!" buttons down towards the middle of the page. A good, solid firewall program should protect you from every single one of the test attacks (along with using the above UnPnP).