Locky ransomware is not able to encrypt files on modern Windows OS versions, locking files only on older Windows XP & Vista machines. Locky’s return to action is surprising but makes perfect sense. The Necurs group’s long-term plan was foiled last week after security researchers from Kaspersky Labs found a flaw in Jaff’s encryption routine and created a free utility to help infected victims recover their files without paying the ransom. This switch most likely happened because Locky encryption was never cracked, and operators have a better chance of extorting ransom.
Source: https://www.bleepingcomputer.com/news/security/locky-ransomware-returns-but-targets-only-windows-xp-and-vista/