#2) Ad-Aware Free Antivirus+ 11

Operating system: Windows XP/Vista/7/8
Price: Free; paid upgrade available

Lavasoft gave Ad-Aware Free Antivirus+ 11 a total user-interface makeover.  Two engines work together to stop malware from traditional viruses to the latest spyware attacks. It provides automatic updates frequently so that your computer and files remain protected from the evolving threats of the web. When comes to web browsing, Ad-Aware Safe Browsing will immediately warn you of the site's risk status, if you click on any dangerous link while browsing or reading an e-mail.

Also, Ad-Aware is one of the first free antivirus software to include a game mode. In this mode, your computer stays protected while you enjoy your favourite games or watch movies without any interruptions. With less than 1 percent CPU utilization, this antivirus won’t slow down your PC even under heavy use.

Pros: This attractive user interface blocks quite a few brand-new malicious URLs.
Cons: former edition scored high in the same malware-blocking test.

Read More: World's 10 Most Innovative Big Data Companies