Prevx is a Full Cloud Anti-Malware meaning that you do not download any definitions there all in the cloud! But if you are looking to buy I would suggest Webroot SecureAnywhere which uses the same tech plus much, much more and Webroot owns Prevx since Nov 2010! http://www.webroot.com/En_US/pr/momentum/corp/technology-acquisition-cloud-security-110110.html http://www.webroot.com/En_US/consumer-compare.html TH