Panda Cloud Antivirus is a unique entry in the free antivirus race. Most free antivirus products still rely on signature updates to detect new malware, but Panda's program instead uses fresh data about malware direct from Panda's servers. As a result, Cloud Antivirus put up some excellent results in some malware detection tests, but its scan speeds were slower than we would have liked to see.

Panda Cloud Antivirus's main interface is really simple: The main window has only four tabs that run across the top--one for the status screen, plus tabs for the scanner, the

scan report, and the recycle bin (where neutralized files live--Cloud Antivirus lets you recover files in case it neutralizes something you wanted to keep). When you first open Cloud Antivirus, you're presented with a status indicator (a green checkmark if all is well, or a red X if something needs your attention) and a short description of your PC's protection status.

The settings pane is equally simple--press the settings icon in the lower-right corner to open it--but some of its wording could be more helpful.

While Panda Cloud Antivirus doesn't use signatures in the classic sense, it still aced our tests for traditional signature-based scanning and detection methods. It detected 99.8 percent of samples in this test--the highest score among the free antivirus products we looked at.

Cloud Antivirus 1.0 struggled some at blocking actual, live malware attacks from malicious Websites or e-mails: It completely blocked 68 percent of attacks--one of the lower scores in this test--and partially blocked an additional 20 percent.

Note: Panda recently released Cloud Antivirus 1.3, which the company says should improve its blocking of such attacks. We don't yet have test results for the new version of Cloud Antivirus, but when we do we'll update this review.

When it came time to clean up infections, Panda Cloud Antivirus did a good--but not outstanding--job. It detected all test infections, and was able to disinfect all active components of an infection 60 percent of the time. The free antivirus software we looked at removed 68 percent of active components, on average, and no product managed a cleanup rate of over 80 percent.

In addition, Cloud Antivirus removed all components of an infection--including Registry keys and other bits and pieces--50 percent of the time, which was the best showing among the free products we looked at.

Scan speeds, though, lagged well behind the pack. Cloud Antivirus completed a manual (on-demand) scan of 4.5GB of files in 5 minutes, 10 seconds--the slowest time recorded in this test. It also fared poorly in on-access scan tests, which shows how well it can scan files as they're opened or saved to disk: It scanned 4.5GB of files in 5 minutes, 38 seconds, a mere three seconds ahead of the the last-place finisher.

And although its impact on overall PC performance was fairly limited relative to other free antivirus products, Cloud Antivirus significantly slowed startup and shutdown times in our tests. It added over 11 seconds to startup time compared to a PC without antivirus software installed (the average free antivirus product added around 6 seconds to startup time), and over 17 seconds to shutdown time (the average antivirus product added around 13 seconds to shutdown time).

Panda Cloud Antivirus is definitely worth considering on the strength of its signature-based detection tests; however, we can't fully endorse it until we're able to test Cloud Antivirus version 1.3.