Protecting your PC. Bloomberg Boot Camp, a report on today's technology. If you have a computer... you may have already learned the hard way that it's a mistake not to invest in anti-virus software and keep it up to date with the latest virus definitions. That's become a big business for companies like Symantec and Network Associates. Those companies also make what are called firewall programs... designed to shield your computer from outside intruders. If you have an always on high speed cable or DSL connection to the Internet... you're especially vulnerable. A company called Zone Labs has had the biggest market share in the firewall business with its Zone Alarm software. VP Fred Felman says the built in protection Microsoft provides with Windows XP doesn't go far enough...

"The Internet connection sharing firewall that's provided with XP is a simple firewall, provides the same protection as a router. So it protects you from inbound things ... but it doesn't protect you from outbound threats like spyware and Trojan horses."

How do those kinds of threats wind up on your PC?

They are pretty mysterious, but it's pretty obvious when you're surfing around you're downloading things, you're getting things via email. It's really problematic. You might trust something. You might think it's a game, you might think it's some other offer that's exciting to you. You click on it, load it, and then you've got spyware on your machine."

Zone Labs sales have been growing at more than 100 percent a year. It offers software for some basic protection for free on the Web. The premium version of its software sells for under fifty dollars. Bloomberg Boot Camp, I'm Fred Fishkin.