This news will be worrying for Mac users, who have often considered themselves to be immune to cyber attacks. Of course this is not true, however the perception has long been that Windows systems are fair game to cyber attackers, whereas Macs are far more resilient. Ransomware is one of the fastest-growing types of cyber threats, and once a user's files have been encrypted, the only way out is by paying a ransom. This is a very lucrative business model for cyber criminals.