HKCrypt (also known as “Hacked Ransomware”) first appeared in late 2017, and encrypts a victim’s files using the RC4 algorithm, then adds the extension “.hacked” to files. The malware pretends to be running a Windows update, then shows a lock screen telling the victim to contact “payment.hkdecrypt@mail.ru”.

https://decrypter.emsisoft.com/hkcrypt