Webroot Internet Security Essentials keep away malicious software from infecting a clean system, Webroot AntiVirus with AntiSpyware 6 deploys over a dozen "shields"—software agents that detect and prevent specific types of malicious behavior. Most block only malicious programs. A few, such as the Browser Helper Object shield, can be triggered by valid program installations, but these include advice to help the user decide whether or not to block the activity. While all of the shields do their part to protect your system, three are
especially prominent. The Internet Connection shield blocks all access to known dangerous Web sites, whether by the browser or any other program. The Execution shield halts known malware in its tracks, utterly preventing it from running on the system. And the File System shield catches and quarantines malware when it attempts any sort of file manipulation. When I tested Webroot AntiVirus with AntiSpyware 6's ability to protect a clean system, none of the other shields even got a chance to help out.
These three did all the heavy lifting.