The Petya ransomware strain signaled a new escalation for crypto-malware when it surfaced in March. For the first time, ransomware went beyond encrypting files on local and shared drives and instead set its sights on locking up the Master File Table on compromised machines.
Petya did have its shortcomings and before long, researchers were able to develop a tool that recovered some files lost to infections.
The criminals behind Petya, meanwhile, have addressed another weakness where the malware would not execute if it were not granted administrative privileges in order to target the MFT. A new installer for Petya was found and disclosed on Thursday. It comes with a failsafe; if its installer is not granted the privileges it seeks, it instead installs another strain of ransomware known as Mischa.
The original Petya executable came with a manifest that requested administrator privileges, said researcher Lawrence Abrams of Bleeping Computer.