https://tech.newstatesman.com/whitepapers/the-changing-state-of-ransomware

According to ransomware detection reports compiled from F-Secure Labs’ upstream telemetry, ransomware attacks have increased sharply since 2015. 2017 saw the number of ransomware detection reports increase by 415 percent compared with the previous year.

Ransomware campaigns have historically been opportunistic in nature, infecting anyone they can via spam emails, exploit kits and malvertising. But many cyber criminals are becoming more selective in their targets, and tailor their techniques to infect businesses or other organizations.