A relatively new addition to the family of fake malware, fake defragmenters pretend to handle file fragmentation in your hard disk drive, while actually just infecting your computer. Because of their Modus Operandi, they could loosely be classified as ransomware. But what’s new about these is the fact that they don’t pretend to clean your computer from viruses like the fake antivirus programs. Instead, they pretend to optimize system performance.

Depending on the specific type that might have infected your computer, if might exhibit ransomware-like behavior because it might pretend, at the end of the “optimization” that the only way to handle the errors found is to purchase the full version of the program, and will not allow access to your data until you do so.

If it doesn’t behave like ransomware, it at least behaves like scareware, i.e. it will keep popping up messages to the effect that problems found will not be resolved until full version of the program is paid for, and it will tell you your computer is at risk, but it doesn’t particularly hold the data in your computer ransom. It just gets in the way of the normal operation of the computer, and in many cases, it might disable your installed antivirus program, to prevent eradication.

The preferred method of infection used by these fake defragmenters is through malicious websites that will attempt to infect your computer as soon as you access them.

A good, up-to-date antivirus should be able to detect and prevent infection from the relatively recent ones. It’s the really recent ones that might get your computer, which will always be the case with the most recent pieces of malware: antivirus programs that depend on signature files (virus definition files) will always be at risk to miss the most recent infections. This is why, once again, a good security system contains several layers, as explained here.

Be aware of which legit programs are installed in your computer, so you can easily identify a rogue/fake program that is trying to fool you into helping it further infect your computer. And ask an expert if in doubt.