The Internet is full of swindlers, vandals, pranksters, and unscrupulous marketers. When you browse the web or read your email, remember that they.re out there.

Some viruses and trojan horses are set to wipe your hard drive. Others can corrupt important data or make your operating system crash. It's always a good idea to make a regular backup copy of your data in case something happens to your hard drive.

Software vendors are always discovering new bugs in their systems and releasing patches to fix them. Many of the most damaging viruses and trojan horses exploit these bugs. If you use Windows, run Windows Update to make sure that your computer has the latest critical updates.

Hackers regularly scan the Internet looking for unprotected computers. A relatively inexpensive firewall can keep many of them out. Make sure that your Internet router has a firewall built-in, or install a software firewall like ZoneAlarm.

Antivirus programs can catch many trojan horses, as well as viruses. But some antivirus programs use an expensive subscription fee system. AVG Antivirus offers its product to home users for free, and has discounts for nonprofits.

Your computer might be infected by spyware, software that monitors your browsing habits. Many antivirus programs don.t detect or repair spyware because the authors have tricked you into .accepting. the installation by burying the question in fine print. You need a specific spyware removal program, like the free Spybot Search and Destroy.

Microsoft Internet Explorer is full of bugs, and won.t even allow users to block pop-up ads. Mozilla, the free successor to Netscape, allows you to block pop-up ads and stops Flash animations from displaying until you click on them.