How vulnerable are you to hacks?

How do I … determine if my computer is vulnerable to online intrusion or hacking?

Rogue programs or hackers use port testers to find computers on the Web that have open or vulnerable ports. A port is a virtual data connection allowing computer programs to exchange data directly, instead of going through a file or other temporary storage location. An open port leaves your computer exposed to possible misuse.

The current best online tool to test your ports is http://canyouseeme.org/. The tool identifies your public Internet address, then lets you scan your available ports for vulnerability. Highly recommended.