I have been looking for a good antivirus program that will not slow down your computer. I finally found one – http://www.immunet.com. This FREE antivirus program is very lightweight and works well even on older PC’s without a lot of ram and CPU. It also bundles the tried and true Clam AV for the more traditional antivirus scans.
It is cloud based, and uses the power of its network to find malware that would go undetected with other antivirus solutions. They scan each file as it is placed on your system and send the hash to their servers in the cloud. The hash is compared against their database. This allows them to use file reputation to prevent viruses from slipping through encrypted and undetected.
Best of all, it is free!.