A just lately found ransomware pressure known as HybridPetya can bypass the UEFI Safe Boot function to put in a malicious software on the EFI System Partition.
HybridPetya seems impressed by the harmful Petya/NotPetya malware that encrypted computer systems and prevented Home windows from booting in assaults in 2016 and 2017 however didn’t present a restoration choice.
Researchers at cybersecurity firm ESET discovered a pattern of HybridPetya on VirusTotal. They be aware that this can be a analysis mission, a proof-of-concept, or an early model of a cybercrime device nonetheless beneath restricted testing.
Nonetheless, ESET says that its presence is yet one more instance (together with BlackLotus, BootKitty, and Hyper-V Backdoor) that UEFI bootkits with Safe Bypass performance are an actual risk.
HybridPetya incorporates traits from each Petya and NotPetya, together with the visible type and assault chain of those older malware strains.
Nonetheless, the developer added new issues like set up into the EFI System Partition and the power to bypass Safe Boot by exploiting the CVE-2024-7344 vulnerability.
ESET found the flaw in January this yr, The difficulty consists in Microsoft-signed functions that could possibly be exploited to deploy bootkits even with Safe Boot safety energetic on the goal.
Supply: ESET
Upon launch, HybridPetya determines if the host makes use of UEFI with GPT partitioning and drops a malicious bootkit into the EFI System partition consisting of a number of recordsdata.
These embrace configuration and validation recordsdata, a modified bootloader, a fallback UEFI bootloader, an exploit payload container, and a standing file that tracks the encryption progress.
ESET lists the next recordsdata used throughout analyzed variants of HybridPetya:
- EFIMicrosoftBootconfig (encryption flag + key + nonce + sufferer ID)
- EFIMicrosoftBootverify (used to validate appropriate decryption key)
- EFIMicrosoftBootcounter (progress tracker for encrypted clusters)
- EFIMicrosoftBootbootmgfw.efi.outdated (backup of unique bootloader)
- EFIMicrosoftBootcloak.dat (comprises XORed bootkit in Safe Boot bypass variant)
Additionally, the malware replaces EFIMicrosoftBootbootmgfw.efi with the susceptible ‘reloader.efi,’ and removes EFIBootbootx64.efi.
The unique Home windows bootloader can be saved to be activated within the case of profitable restoration, that means that the sufferer paid the ransom.
As soon as deployed, HybridPetya triggers a BSOD displaying a bogus error, as Petya did, and forces a system reboot, permitting the malicious bootkit to execute upon system boot.
At this step, the ransomware encrypts all MFT clusters utilizing a Salsa20 key and nonce extracted from the config file whereas displaying a faux CHKDSK message, like NotPetya.
Supply: ESET
As soon as the encryption completes, one other reboot is triggered and the sufferer is served a ransom be aware throughout system boot, demanding a Bitcoin cost of $1,000.
Supply: ESET
In change, the sufferer is supplied a 32-character key they will enter on the ransom be aware display screen, which restores the unique bootloader, decrypts the clusters, and prompts the person to reboot.
Although HybridPetya has not been noticed in any actual assaults within the wild, related initiatives might select to weaponize the PoC and use it in broad campaigns focusing on unpatched Home windows methods at any time.
Indicators of compromise to assist defend towards this risk have been made obtainable on this GitHub repository.
Microsoft fastened CVE-2024-7344 with the January 2025 Patch Tuesday, so Home windows methods which have utilized this or later safety updates are shielded from HybridPetya.
One other strong follow towards ransomware is to maintain offline backups of your most vital knowledge, permitting free and straightforward system restoration.
46% of environments had passwords cracked, almost doubling from 25% final yr.
Get the Picus Blue Report 2025 now for a complete have a look at extra findings on prevention, detection, and knowledge exfiltration tendencies.
