A just lately found ransomware pressure known as HybridPetya can bypass the UEFI Safe Boot function to put in a malicious utility on the EFI System Partition.
HybridPetya seems impressed by the damaging 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 notice that this can be a analysis challenge, a proof-of-concept, or an early model of a cybercrime device nonetheless below 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 fashion and assault chain of those older malware strains.
Nevertheless, the developer added new issues like set up into the EFI System Partition and the flexibility to bypass Safe Boot by exploiting the CVE-2024-7344 vulnerability.
ESET found the flaw in January this 12 months, The difficulty consists in Microsoft-signed purposes that might be exploited to deploy bootkits even with Safe Boot safety lively 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 embody 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.previous (backup of unique bootloader)
- EFIMicrosoftBootcloak.dat (incorporates XORed bootkit in Safe Boot bypass variant)
Additionally, the malware replaces EFIMicrosoftBootbootmgfw.efi with the weak ‘reloader.efi,’ and removes EFIBootbootx64.efi.
The unique Home windows bootloader can also be saved to be activated within the case of profitable restoration, which 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 notice throughout system boot, demanding a Bitcoin cost of $1,000.
Supply: ESET
In change, the sufferer is offered a 32-character key they will enter on the ransom notice 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 concentrating on unpatched Home windows techniques at any time.
Indicators of compromise to assist defend in opposition to this risk have been made accessible on this GitHub repository.
Microsoft fastened CVE-2024-7344 with the January 2025 Patch Tuesday, so Home windows techniques which have utilized this or later safety updates are protected against HybridPetya.
One other stable follow in opposition to ransomware is to maintain offline backups of your most vital knowledge, permitting free and simple system restoration.
46% of environments had passwords cracked, practically doubling from 25% final 12 months.
Get the Picus Blue Report 2025 now for a complete take a look at extra findings on prevention, detection, and knowledge exfiltration developments.
