Panda Security, the Spain-based antivirus software, today released a new free antivirus program called Panda Cloud Antivirus. The "Cloud" appellation comes from its sending data about files to Panda servers on the Internet for scans, instead of using your PC's resources.
Cloud Antivirus will send a file's signature and heuristic data (see below) up to Panda servers, which evaluate the info to decide whether the file is harmful or not. Panda's servers take in files from user submissions, honeypots, and other sources to construct its signature and scan database, but the free client won't send the actual file from your PC.
If you don't have an Internet connection it will scan using a cache of data on your PC, but Panda says that cache is only a small sub-set of the information used to scan by its online servers. So you'll need an Internet connection for the app to be fully effective.
Also, the program will evaluate a new file heuristically, but not behaviorally. That means it will look into the file and gauge its characteristics beyond its signature, but it won't attempt to evaluate what it actually does when run (in a protected sandbox environment, for example). If you decide to try Panda's app and want to add behavioral detection, you could install the also-free Threatfire, which should be able to run alongside it.
In an attempt to improve performance, Cloud Antivirus will only block access and immediately scan when a file is opened or a program tries to run. Downloads from the Internet will be scanned right away, but won't be locked pending the scan. And files sitting on your hard drive will only be scanned in the background while your computer is idle.
If a downloaded file, or one on your hard drive, is opened or run, then it gets the high-priority, file-locking scan. Panda says this approach should improve performance by only taking aggressive action when it is most needed.
Panda says it is offering the app for free so it can increase North American market share for its products, and also so it can use anonymous data from free users to improve the efficacy of its scans. It will add paid services on top of the free product, it says.
I'll be very interested to see some independent test results for Cloud AV's detection and performance to see how it stacks up against other antivirus apps, particularly the small handful of free programs. For more information on how Panda's new app works, see http://blog.cloudantivirus.com/.