These organizations test Anti-Virus products. Their tests are generally attempts to determine which product detects the most viruses.
The tests performed by these organizations can't actually tell you which Anti-Virus is best because there is no best. They can only tell you which ones are very good and which ones aren't.
These organizations don't have all the viruses there are so they can't tell you which product detects the most viruses, only which product detects the most viruses in their collection (zoo).
Also, since new viruses are being made daily, the real-life detection capability of an AV product will change over time, and it's detection capability relative to other products will change each time one of the products is updated (which happens anywhere from once a week to once every month or two).
Finally, these organizations don't test all aspects of an Anti-Virus product, and for good reason sometimes as some aspects are difficult if not impossible to quantitatively evaluate. These are all reasons why there can be no single best Anti-Virus product.
last modifed june 8 2000 : this page hand crafted by kurt wismer