Once installed on either a computer or (more increasingly) a mobile device they can take all your files and lock them away, effectively holding them ransom until you pay the hackers a fee.
Ranging from £200 all the way up to £1000 these fees are almost always required in Bitcoin and are always priced in such a bracket that many customers will feel they're forced to take this one off hit.
Senior Security Researcher, Kaspersky Lab David Emm recommends that you should never pay these ransoms. Not only do they validate ransomware as a business model but there's absolutely no guarantee that you won't be hit again by a different piece of software.
So how does ransomware work?
Typically the software is hidden inside an email. Once the email is opened the virus is installed onto the computer, it will then either search for important personal information or simply lockdown the entire computer.
Once installed the software then demands that the user pays a ransom and in return the victim regains control of their computer.
While it's most typically found on computers and laptops there are increasing reports of ransomware being found on smartphones.
One such piece of software uses the front-facing camera on the phone to take a picture of the victim, it then locks the phone claiming that the person was viewing child pornography.
The contents of the smartphone is then completely locked unless a fee of $500 is paid.
How to protect against ransomware?
As Newsy's video above explains, there are a number of ways you can protect yourself.
The most obvious is keeping a close eye on your incoming emails. While spam filters can do a lot of the groundwork it still takes vigilance to make sure that you don't accidentally open a particularly well-hidden spam email.
Secondly there are now a host of programs and apps which can protect both your phone and computer from these emails.
Apps like Focus by Firefox can help protect against unwanted pop-ups on your smartphone while also speeding up your browser.
Focus isn't just an ad-blocker though, it's also capable of preventing potentially harmful pop-ups from appearing and then subsequently asking for access to your device.