Active Shield guards each and every place in your system where infection can come from and where it can take roots:

System folders - Active Shield guards system folders and warns about any changes inside them (copy, creation or deletion of files). It will also try to restore deleted critical system files. This feature prevents a lot of trojans and spyware (even unknown) from installing into your system.

Autorun list - Active Shield guards autorun list (the list of files that run automatically in Windows startup - a lot of trojans and spyware can be run from this place) and warns about new suspicious autorun items.

Processes - Active Shield guards currently ran processes and warns about malicious processes (using its large database of known threats). This feature kill salmost all known malicious programs when they are active.

Browser settings - Active Shield guards your browser's settings and alerts when they are changed. These settings include home page, security options, etc.

Possibly malicious files and folders - Active Shield scans PC for known malicious files and folders.

Registry - Active Shield scans system registry for known malicious keys and values.

Cookies - Active Shield monitors tracking cookies being installed in your system by different sites and warns about malicious ones.