The REvil (also known as Sodinokibi) is a Ransomware-as-a-Service (RaaS). The first attack of REvil in middle of April 2019, and attracted huge attention span from the InfoSec world due to their uncanny similarities with GandCrab Ransomware. The group uses different distribution techniques of deploying ransomware such as exploit kits, scans and exploiting various vulnerable software (Oracle WebLogic), RDP servers, and backdoored software installers. Revil has made estimated over $100 million by infecting large business owners and they threaten to publish data if the ransom money is not paid by the victim.
The ransom note placed by REvil (Source: Elliptic)