Ransomware is the fastest growing form of computer malware, experts warn.
It's a malicious virus that locks the user out of their computer and demands a fee to return their files.
A report published by the Australian government claims 72% of businesses surveyed experienced ransomware incidents in 2015.
The figure was just 17% in 2013 .
It's also a growing threat for mobile devices as it can be hidden in an app, says Gert-Jan Schenk, vice-president at internet security company Lookout.
