Security Experts:

Upgraded Petya Malware Installs Additional Ransomware

Petya, a piece of malware observed in late March to encrypt the entire hard drive o infected computers, has received an update and is now dropping a second ransomware, researchers warn.

When spotted roughly two months ago, Petya was observed performing a two-stage encryption, with the first step involving gaining Administrative privileges on infected computers. Should this initial operation fail, the malware would not harm the compromised machine, researchers said at the time.

However, should it gain admin privileges, the ransomware could modify the master boot record and could move to the second phase, which involved rebooting the system and executing a fake check disk to destroy the file system and encrypt the partition table, preventing users from accessing their files.

In the updated Petya variant, users are no longer safe from infection if the malware doesn’t manage to receive administrative privileges, Bleeping Computer’s Lawrence Abrams explains. The malicious program still requires those privileges to perform its function, but if unsuccessful, it drops a second ransomware, which can encrypt files without such privileges.

Dubbed Mischa Ransomware, this piece of malware works just as other similar ransomware out there does: it scans drives for specific files, encrypts them using AES-encryption, and then appends a 4 character extension to the filename. The malware also stores the encrypted decryption key at the end of the encrypted file and asks for a 1.93 Bitcoin (around $875) ransom.

Researchers discovered that Mischa also encrypts .exe files, in addition to the usual file types targeted by the different ransomware families out there. On its payment website, the ransomware presents a payment wizard to users, taking them through each step of making the ransom payment, starting with the entering of a personal code that has been included in the victim's ransom note. The site also includes a support page that can be used to ask the malware developers questions and a FAQ.

The Petya/Mischa installer is being distributed via spam emails that pretend to be job applications and which contain a link to a cloud storage service that point to a supposed image of the applicant and to an executable with a name that starts with PDF. When the victim launches the executable, it tries to install Petya and gain admin privileges and, if that fails, installs the Mischa Ransomware.

 

Unfortunately, victims of these ransomware variants have no means of decrypting and restoring their files for free, although they could use backups and Shadow Volume Copies to restore older versions of their files. As always, users are advised to keep their computer’s software updated and to avoid opening links or documents coming from unknown sources.

Over the past several months, ransomware has become a formidable enterprise threat, as cybercriminals have upped their game and increasingly target organizations around the world. Cybercriminals are also updating their code to increase infection rates via new delivery mechanisms or to transform existing Trojans into ransomware.

 

Related: Paying Not an Option When Ransomware Hits

Related: Ransomware: Four Ways to Assess This Growing Threat as a Business Risk

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