A newly discovered variant of MegaCortex ransomware goes well beyond just encrypting victims' files -- it also changes their Windows passwords and threatens to publish their stolen data if they fail to pay.
"All of your user credentials have been changed and your files have been encrypted," the ransomware note warns infected victims. Both threats are true: files are encrypted and given an .m3g4c0rtx extension, and victims who attempt to log in to their system will find that they cannot. Instead, all they will see is a legal notice that says "Locked by MegaCortex," along with the attacker-controlled email addresses to contact.
The credential change is made possible by executing the net user command when the ransomware is executed, BleepingComputer reported, citing Kremez.
The ransom note also makes a second threat: "We have also downloaded your data to a secure location. In the unfortunate event of us not coming to an agreement, we will have no choice but to make this data public." It is has been confirmed if the MegaCortex attacks actually have this capability.
The file encryption is reportedly conducted by two extracted DLL files, while a trio of CMD files are leveraged to remove shadow volume copies, wipe free space on the C: drive, create the aforementioned legal notice and clean up the malicious files.