Reinstalling out-of-date virus checkers can be risky, as it can be to spyware what a pool of water is to mosquitos: A perfect breeding ground for more problems.

As of late 2004, PCs are far more likely (e.g., tens to hundreds of times) to be attacked by spyware than they are to be attacked by traditional viruses. This speaks well of the effectiveness of virsus checkers, since they have done a good job of reducing the frequency of virus infections in the Internet. However, from a practical viewpoint it also means that most people are putting too much time, money, and trust into the wrong kinds of protections for their PCs.

If you have a good firewall, active spyware guards, and good email hygene (the latter point cannot be emphasized enough!), it is possible to go for weeks, months, or longer without getting hit by a virus. For such low infection rates, an online virus checker such as Trend Micro's Housecall can do the job nicely, while minimizing the amount of resident software in which clever spyware might rake up residence. I was surprised at just how viable this option is. In sharp contrast, attempting to run a PC on a DSL line in late 2004 without the benefit of good firewalls and active antipyware guards comes close to being a form of privacy and performance suicide.

If you choose to reinstall your virus checker, be sure it is both current and under a valid subscription. Get a recent CD copy if at all possible, since repeated online upgrades over a period of months or years can dramatically increase the overall risk that spyware will get in at some point and subvert your checker.

Finally, an important point: Do not let old virus remain on your computer. If your subscription has expired, remove the virus checker. Don't let it become a breeding ground for spyware. For example, have you ever had a virus checker that seemed to keep updating itself long after your subscription had expired? While vendors sometimes really are generous, magical out-of-subscription updates can also be a sign that your expired virus updater has been hijacked by spyware, and is now busily downloading software that has nothing whatsoever to do with protecting you from viruses.