BlackNET RAT is a modern open source remote access Trojan written in VB.net with it's command and control back-end is written in beautiful admin panel written in PHP.
BB Ransomware "pretends" to encrypt user data and then requires to send bitcoins to the BTC address in order to return the files. In fact, the files are not encrypted at all added with .encryptedbyBB extension.
CoViper is just another threat actor that wants a piece of the 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 advanced computer user can recover it by installing a new MBR.
Malicious hacker finds a way to capitalize the current corona virus epidemic. They send fake phishing emails appear to be from government about a corona relief package.
Nephilim Ransomware is the newest of the Nefilim and Nemty ransomware. Almost all of the code base is same of all of them with minor changes.