Ransomware is malicious software that locks you out of your computer or your data, and demands money to let you back in.
One "brand" of ransomware, widely known as Reveton, has been very widely circulated in recent months.
Reveton pretends to be a warning from your country's national police service, locks you out of your PC, and threatens criminal proceedings within 48 hours - usually for unspecified copyright offences.
Of course, you can bypass the prosecution if you pay a "fine" to the cybercriminals. The amount they extort is typically about $200.
If you run across this sort of malware, it's tempting just to wear the cost and hope that the crooks live up to their promise of giving your PC back.
We recommend that you don't do that, so here's a short video to advise you, and your friends and family, on what to do instead:
(Enjoy this video? Check out more on the SophosLabs YouTube channel.)
Remember: an up-to-date and active anti-virus, combined with prompt software patching to close known holes, makes things much harder for the Bad Guys.
So give yourself the best chance of safety by taking security seriously!