RAT
Cyrat
According to gdatasoftware, Cyrat ransomware uses Fernet to encrypt files.
Cyrat is a Windows rat.
Background
G DATA notes that Cyrat ransomware relies on Fernet to encrypt victims' files. Fernet is a symmetric scheme designed for small data files that can be held entirely in RAM. Although Fernet itself is a legitimate and common library, its use in ransomware is unusual and, in this instance, proves problematic.
Source: Malpedia (Fraunhofer FKIE).