MedusaLocker Ransomware encrypts user data using AES + RSA-2048, and then requires victim to be sent an email to purchase the decryption program. The project file says: MedusaLocker.pdb. A "Medusa" section is also created in the registry.
CoronaLocker is another malware related to COVID-19. It is screen locker distributed via a fake WiFi hacking program named wifihacker.exe. Upon execution it lock user out of windows. After logging again it make looping sound produce by the Microsoft Speech API saying corona virus.
CoViper is just another threat actor that want a piece of pie of the COVID-19 outbreak. CoViper is a Master Boot Locker or MBRLocker. It means it does not encrypt user files but change the Booting "sequence" and hence render a system useless. An advance computer user can recover it by installing a new MBR.