The new version, Malwarebytes Anti-Malware Premium, is a pretty radical rework of the software. Take a look at the Best free antivirus software. It has rescued machines in this reviewer's care on more than one occasion, detecting and removing threats either not flagged up by conventional AV software, or cleaning out those 'hard to shift' attacks.

Instead of using signatures of know viruses, it works only by looking at virus-like behaviour from new software that you introduce to your Windows PC. Not a traditional antivirus program as such, it works behind the scenes to provide extra protection, claiming to get at the malware many internet security suites don't hit. Malwarebytes Anti-Malware is a bit of an oddball.