Portscanning your Computer

Ports are like the "channels" that come on your internet connection. In the early days of the web, they were all open, and anybody could reach out and touch someone on any of these ports. Today, by default, these ports closed by virtue of your computer's firewall.

It goes without saying that your computer should be behind a hardware firewall, which these days usually come on your router. Not the router your cable or telephone company provided, but the one you have connected between that & your computer. You have one, right?

If not, GRC is a good resource for how to configure these routers, and will even "portscan" your computer for you for free, without downloading anything (scroll down to "ShieldsUp!")