As cloud, the US headed the list with just over 2,000 infections, ahead of Germany on 1,203, and Hungary on 561. Other countries reporting in the hundreds include France, Russia, Australia, Italy and Taiwan.

This volume of infections isn't large by comparison with other types of malware but ransomware doesn't set out to hit large number of people at any one time. The modus operandi is to attack smaller numbers using below-the-radar campaigns, extracting relatively large amounts from each victim.

The extent of ransomware's success can only be gauged by the growing volume of attacks, which implies a worthwhile success rate.

Ransomware is really the ultimate form of social engineering malware in that people are invited to agree to defraud themselves. The trick is to get people to believe there is no alternative to agreeing to their malware's terms.

After existing at very low levels for years, ransom attacks suddenly started to spike in mid-2010, examples of which include an attack in which Windows users were and asked for a $143 (£91) payment.