How secure is your computer? If you'd like to see if someone can hack into it, go to Gibson Research and run the "Shields Up!" test. Steve Gibson is a world-class expert at matters of Internet security and his independent research has forced many software makers to fix loopholes in their products. He has also alerted the world to the dangers of "spyware," which is software that — unbeknown to you, its user — is recording and transmitting information on your buying or browsing habits to some company out there. Gibson's Opt-Out program, which you can download at his site, will identify some of the spyware, if any, on your computer. And if that matters to you, you might also want to download and run Ad-Aware (which you can do here) which is from another maker and which locates and removes other spyware.