The FBI issued a flash alert at the beginning of the month to alert organizations of the new threat actor. The FBI said that its targets in the US include healthcare, government, financial, and retail sectors. The malware started as PwndLocker in late 2019 but made a reputation by targeting businesses and local governments, adjusting its ransom demands to the size of the compromised network. With ransom demands between $175,000 to over $660,000, ProLock is as serious a threat as other, more infamous ransomware families like Maze, Sodinokibi, Ryuk or LockerGoga.
Source: https://www.bleepingcomputer.com/news/security/fbi-warns-of-prolock-ransomware-decryptor-not-working-properly/