Three years ago there was alarming development in the computer security world. The first piece of viable ransomware arrived and has been slowly making a bigger and bigger impact.

When viruses started being written in the 90s they might lock up your machine or play a joke on you but they rarely did serious harm. In the 00s they evolved to take control of your computer’s unused processes to give the controlling hacker botnets that let the hacker attack more machines online but it was still rare that they directly impacted the individual user.

The first ransomware, Cryptolocker changed that. When the program and the many copycats now out there get onto your computer it goes through every file on your hard disk without you seeing and encrypts anything that might be of value to you. This is all your Word and Excel documents, every picture, every video, every game save file, every configuration setting – in short everything you’ve generated or store on your pc. It spreads out to every connected hard disk and through your local network and when it’s done encrypting presents you with a choice – send money to a certain bitcoin address within a short period of time and get the key to your files or lose them forever.

It holds your files to ransom.

So how can you prevent getting stung?

The safest answer is to keep decent backups. These backups should be on a drive or remote cloud system that is not regularly connected but yet is up to date. Just storing files in Dropbox or Google Drive won’t work as they’re hooked into your PC and hence will get encrypted as well. It’s hard to point to a specific safe system as different types of files can be backed up in different ways.

For example, if you want to keep your images backed up Flickr offers a terabyte of free private storage and will not be affected by this. Audio files could be backed up to Google Music’s free fifty thousand mp3 storage and the best standby for those super crucial files – copy them to a USB thumb drive and keep it unplugged. If this sounds like a lot of work there is one automatic fix – get a cloud backup with versioning. If you get this then even if it does manage to spread to and encrypt files stored there then the older versions will be safe.

I’ve been asked if regular virus scanners do any good and the unfortunate answer is no – not much. Keeping yourself completely patched and up to date will help – if you’re running on Windows turn on Recommended updates and let Microsoft handle it.

Finally, if you’re unlucky enough to get infected you can try paying. The cost is usually somewhere between £200 and £400 which, depending on your data, might be worth it to you. Be aware there is no guarantee of getting your files back and even if you do you might be hit by ransomware again the next day.