Comodo's performance in our real-world tests was acceptable: It blocked 78.6 percent of new malware, slightly above average compared with other free antivirus programs. It partly blocked an additional 21.4 percent of attacks. But Comodo protected poorly against well-known malware. It detected 98.2 percent of zoo samples. Though that may sound like a good score, only two of the nine 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 percent 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. Although its included firewall makes Comodo Internet Security Premium appear attractive, we'd suggest giving other freebies a look first.