PC Tools AntiVirus Free didn't slow overall system performance much. Its results were mixed when we tested scan speeds, though: Its on-demand scanner completed our tests in a sluggish 4 minutes, 51 seconds. On the other hand, the on-access scanner finished in 2 minutes, 50 seconds, the second-best time of all the products we tested.
PC Tools is easy to use for the most part, and its screens are laid out nicely. One thing I found annoying, however, was that it pushed the paid version of the company's software at every turn.
Comodo Internet Security Premium
Comodo Internet Security Premium 5.9 has an accessible interface, and it comes with a firewall (it's the only freebie we tested that has one), but in both malware blocking and cleanup, it ranks behind other free antivirus products we tested. (Note: This link goes to the download for Comodo Internet Security 5.10 in PCWorld's Downloads library.)
Comodo's performance in our real-world tests was acceptable: It blocked 78.6% of new malware, slightly above average compared with other free antivirus programs. It partly blocked an additional 21.4% of attacks. But Comodo protected poorly against well-known malware. It detected 98.2% of zoo samples—though that may sound like a good score, only two products we tested performed worse.
Malware cleanup may be Comodo's Achilles' heel: It detected all infections, but it was successful in disabling malware only 80% of the time—quite low compared with the top performers. It left behind more malware remnants than any other product, too; it was successful in removing all traces of malware only a third of the time.
For the most part, Comodo had a light impact on PC performance, but it significantly slowed copying of files across the network. Comodo also took its time in scanning files for threats: Its on-demand scanner took 4 minutes, 31 seconds—the third-slowest result. Meanwhile, the on-access scanner required a staggering 13 minutes, 58 seconds to run, nearly twice as long as the next-slowest product. While its included firewall makes Comodo Internet Security Premium an attractive option, we'd suggest giving other freebies a look first.
Here are three products to consider as supplements to your main antivirus software.
PC Tools Threatfire
PC Tools Threatfire won't replace your existing antivirus software, since it won't effectively clean up malware that has already infected your computer. What it will do, however, is excel at preventing brand-new threats from infiltrating your system.