In theory, cloud-based security apps have two distinct advantages over desktop security suites. The primary advantage is that cloud-based software eliminates the need to run frequent threat-signature updates. Daily patch updates get annoying fast, and many users wind up tuning out the nag notes popping up from their system tray until the security software becomes too outdated to protect the PC. And since desktop suites typically don't update more than once a day, they can't offer the same kind of up-to-the-minute set of threat signatures that cloud-based security can.

The second advantage--again, in theory--is that cloud security software places most of the work of scanning files onto remote servers, rather than using your PC's resources. The expectation here is that running a lean, lightweight desktop app that outsources most of the processing to the cloud should benefit your overall system performance.

In practice, the cloud security apps we've tested have performed adequately, but have failed to blow their desktop-centric competitors out of the water. The cloud-based and services both delivered decent protection in our recent --but neither managed to block more threats than the winning package, the desktop-based Norton Antivirus 2011. Also disconcerting for cloud advocates is the fact that neither of these Web-centric antivirus apps outshone the best of the desktop suites in their impact on a PC's performance.

Like most of the other I've discussed in this article package, however, cloud security is a young category. We fully expect to see the performance and features of these suites improve rapidly over the coming years, especially as the leading desktop competitors move their services to the cloud as well.