Malware
Mespinoza
aka pysa
Mespinosa is a ransomware which encrypts file using an asymmetric encryption and adds .pysa as file extension.
Mespinoza, also known as pysa, is a Windows malware family.
Background
Mespinosa is a ransomware that encrypts files with asymmetric encryption and appends the .pysa extension. Dissectingmalware suggests the "pysa" name likely comes from the Zanzibari coin of the same name.
Source: Malpedia (Fraunhofer FKIE).