A Wall Of FireHackers are crashing Web sites daily, but you can stop them from hacking yours.

Katherine Gaudette learned the hard way that her company's Web site was vulnerable to an attack by hackers. Founder of Capetown-Rio Inc., a 12-person marketing communications firm located in Redmond, Washington, Gaudette thought she was safe when she implemented a firewall security device (a mix of software and hardware designed to keep out unauthorized Internet users) early last year to protect her company's network from computer hackers. "When we work with customers, we're acting, in essence, as their counselors," says Gaudette, 35. "So we have to make sure what we're doing with them doesn't get shared with anybody else."

But while her firewall held just fine, the ISP hosting her Web site didn't have one. Her Web site was hacked in August--a computer thug entered Capetown-Rio's Web server and deleted key information about some promotional campaigns for major clients.