The master decryption key for last year’s Petya ransomware was made public last week and has since been confirmed to be genuine.
Petya ransomware first emerged in March 2016, distinguishing itself from similar malware by encrypting the Master Boot Record (MBR) instead of individual files. Soon after its initial appearance, Petya was paired with another ransomware, and the pair became available as a service a couple of months later.
The last known variant of the malware was spotted in December 2016 and was referred to as GoldenEye. Dubbed PetrWrap, a ransomware family observed in March this year was using Petya for its nefarious purposes, but wasn’t created by Janus Cybercrime Solutions, the name Petya’s author goes by.
NotPetya, the destructive wiper that hit numerous organizations in Ukraine and various other countries in late June, wasn’t the work of Janus either, but only borrowed code from Petya. In a tweet on June 28, Janus claimed no connection with NotPetya.
One week later, on July 5, the ransomware author posted a link to an encrypted and password protected file hosted on the mega.nz service. After opening the file, independent researcher and programmer Hasherezade found in it the master decryption key for all previous Petya variants.
Kaspersky security researcher Anton Ivanov has already confirmed that the key works for all Petya versions, including GoldenEye.
The release of the master decryption key is great news for those Petya victims who were unable to restore their files to date. Last year, security researchers managed to crack the first two versions of the ransomware, and the only variant not decrypted before was GoldenEye.
“Thanks to the currently published master key, all the people who have preserved the images of the disks encrypted by the relevant versions of Petya, may get a chance of getting their data back,” Hasherezade explains.
The newly released master key, however, won’t help users hit by NotPetya.
“This key cannot help in case of [NotPetya], since, in this particular case, the Salsa keys are not encrypted with Janus’ public key, but, instead of this, erased and lost forever. It can only help the people who were attacked by Petya/Goldeneye in the past,” Hasherezade notes.
Although the wiper’s alleged authors suggested last week they could provide decryption keys to help users with encrypted files, some researchers suggest decryption isn’t possible in NotPetya’s case. Others, however, explain decryption is possible if NotPetya was “unable to obtain administrator privileges when running.”
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