Petya/NotPetya copycat with UEFI Safe Boot bypass

ESET Analysis has found HybridPetya, on the VirusTotal pattern sharing platform. It’s a copycat of the notorious Petya/NotPetya malware, including the aptitude of compromising UEFI-based programs and weaponizing CVE‑2024‑7344 to bypass UEFI Safe Boot on outdated programs.

Key factors of this blogpost:

• New ransomware samples, which we named HybridPetya, resembling the notorious Petya/NotPetya malware, had been uploaded to VirusTotal in February 2025.
• HybridPetya encrypts the Grasp File Desk, which comprises vital metadata about all of the information on NTFS-formatted partitions.
• Not like the unique Petya/NotPetya, HybridPetya can compromise fashionable UEFI-based programs by putting in a malicious EFI utility onto the EFI System Partition.
• One of many analyzed HybridPetya variants exploits CVE‑2024‑7344 to bypass UEFI Safe Boot on outdated programs, leveraging a specifically crafted cloak.dat file.
• ESET telemetry exhibits no indicators of HybridPetya getting used within the wild but; this malware doesn’t exhibit the aggressive community propagation seen within the unique NotPetya.

Overview

Late in July 2025, we encountered suspicious ransomware samples, uploaded to VirusTotal from Poland, underneath numerous filenames, together with notpetyanew.exe and different related ones, suggesting a reference to the infamously damaging malware that struck Ukraine and lots of different nations again in 2017. The NotPetya assault is believed to be essentially the most damaging cyberattack in historical past, with greater than $10 billion in whole damages. Regardless of NotPetya’s similarity to the Petya ransomware, first found in March 2016, NotPetya’s goal was pure destruction, as encryption key restoration from the sufferer’s private set up key was not doable. Due to the shared traits of the presently found samples with each Petya and NotPetya, we named the brand new discovery HybridPetya.

Whereas ESET telemetry exhibits no energetic use of HybridPetya within the wild, one vital element in these samples nonetheless caught our consideration – not like the unique NotPetya (and Petya ransomware as effectively), HybridPetya can also be able to compromising fashionable UEFI-based programs by putting in a malicious EFI utility to the EFI System Partition. The deployed UEFI utility is then answerable for encryption of the NTFS-related Grasp File Desk (MFT) file – an vital metadata file containing details about all of the information on the NTFS-formatted partition.

After a bit extra digging, we found one thing much more fascinating on VirusTotal: an archive containing the entire EFI System Partition contents, together with a really related HybridPetya UEFI utility, however this time bundled in a specifically formatted cloak.dat file, weak to CVE‑2024‑7344 – the UEFI Safe Boot bypass vulnerability – that our crew disclosed in early 2025.

Curiously, regardless of the filenames on VirusTotal and the format of the ransom word within the present samples suggesting that they is perhaps associated to NotPetya, the algorithm used for the technology of the sufferer’s private set up key, not like within the unique NotPetya, permits the malware operator to reconstruct the decryption key from the sufferer’s private set up keys. Thus, HybridPetya can function common ransomware (extra like Petya), reasonably than being solely damaging like NotPetya.

Curiously, on September 9^th, 2025, @hasherezade revealed a submit in regards to the existence of a UEFI Petya PoC, with a video demonstrating execution of the malware with UEFI Safe Boot enabled. Despite the fact that the pattern from the video is clearly completely different from the one offered on this blogpost (displaying the standard Petya ASCII artwork cranium, which isn’t current within the samples we found), we suspect that there is perhaps some relationship between the 2 instances, and that HybridPetya may additionally be only a proof of idea developed by a safety researcher or an unknown risk actor.

On this blogpost, we concentrate on the technical evaluation of HybridPetya.

HybridPetya technical evaluation

On this part, we offer a technical evaluation of HybridPetya’s elements: the bootkit and its installer. We additionally individually dissect a model of HybridPetya that’s able to bypassing UEFI Safe Boot by exploiting CVE-2024-7344. Observe that HybridPetya helps each legacy and UEFI primarily based programs – on this blogpost, we’ll concentrate on the UEFI half.

Curiously, the code answerable for producing the victims’ private set up keys appears to be impressed by the RedPetyaOpenSSL PoC. We’re conscious of at the very least one different UEFI-compatible PoC rewrite of NotPetya, dubbed NotPetyaAgain, which is written in Rust; nonetheless, that code is unrelated to HybridPetya.

UEFI bootkit

Disk encryption

If the worth of the encryption flag is 0, the bootkit extracts the 32-byte-long Salsa20 encryption key and 8-byte-long nonce from the configuration information, and subsequently rewrites the configuration file, now with the encryption key zeroed and the encryption flag set to 1. It continues with encryption of the EFIMicrosoftBootverify file with the Salsa20 encryption algorithm utilizing the important thing and nonce from the configuration. Then, earlier than continuing to its most important performance – disk encryption – it creates the file EFIMicrosoftBootcounter on the EFI System Partition; the aim of this file is defined later.

The disk encryption course of begins with identification of all NTFS-formatted partitions. As proven in Determine 2, the pattern does so by getting the checklist of handles for linked storage units, figuring out the person partitions by checking that EFI_BLOCK_IO_MEDIA->LogicalPartition is TRUE, and eventually verifying whether or not the partition is NTFS formatted by evaluating the primary 4 bytes of the information current within the first partition’s sector with the NTFS signature NTFS.

As soon as the NTFS partitions have been recognized, the bootkit continues with encryption of the Grasp File Desk (MFT) file, the important metadata file containing details about different information and the situation of their information on the NTFS-formatted partition. As proven in Determine 3, through the encryption, the bootkit rewrites the contents of the EFIMicrosoftBootcounter file with the variety of already encrypted disk clusters, and updates the faux CHKDSK message displayed on the sufferer’s display screen (proven in Determine 4), with the details about the present encryption standing (although, primarily based on the message, the sufferer could imagine that the disk is being checked for errors, not being encrypted).

When completed with the encryption, the bootkit reboots the machine.

Disk decryption

If the bootkit detects that the disk is already encrypted, that means that the worth of the encryption flag from the configuration file is 1, it exhibits the ransom word proven in Determine 5 or Determine 6 (relying on the bootkit model), and asks the sufferer to enter the decryption key. Observe that whereas the HybridPetya ransom word has the identical format as that of the unique NotPetya (proven in Determine 7), the ransom quantity, bitcoin deal with, and the operator’s e-mail deal with are completely different. Additionally, the model deployed with the UEFI Safe Boot bypass makes use of a distinct contact e-mail deal with (wowsmith999999@proton[.]me) than the model deployed by the obtained installers (wowsmith1234567@proton[.]me). It’s value mentioning that the bitcoin deal with is identical in each variations.

When a key with the proper size – 32 characters – is entered and confirmed by the sufferer urgent Enter, the bootkit proceeds to verification of the important thing. As depicted in Determine 8, key validity is established by trying to decrypt the aforementioned EFIMicrosoftBootverify file with the equipped key, and checking whether or not the plaintext comprises solely bytes with worth 0x07. Observe that the bootkit variant deployed by way of the UEFI Safe Boot bypass hashes the equipped key with an algorithm most likely primarily based on SPONGENT-256/256/16, utilizing that hash worth because the decryption key, whereas the bootkit deployed by the obtained installers takes the person’s enter as is.

If the proper secret is entered, the bootkit updates the configuration file with the encryption flag worth set to 2 and in addition fills within the decryption key. Then it reads the contents of the EFIMicrosoftBootcounter file (containing the variety of disk clusters beforehand encrypted) and proceeds with disk decryption. For the decryption, the bootkit proceeds with a really related course of to that of NTFS partition discovery and MFT decryption (the Salsa20 encryption and decryption course of is identical) as described within the Disk encryption part. The decryption stops when the variety of decrypted clusters is the same as the worth from the counter file. Throughout the means of MFT decryption, the bootkit exhibits the present decryption course of standing, depicted in Determine 9, on the sufferer’s display screen.

Subsequent, the bootkit proceeds with recovering the authentic bootloaders EFIMicrosoftBootbootmgfw.efi and EFIBootbootx64.efi from the backup file beforehand created through the set up course of: EFIMicrosoftBootbootmgfw.efi.outdated.

Lastly, after the decryption course of is completed and the authentic bootloaders recovered, the bootkit prompts the sufferer to reboot the machine (Determine 10). If every little thing went effectively, the machine ought to begin the working system efficiently after the reboot.

Deploying the UEFI bootkit element

On this part, we concentrate on the bootkit-installation performance of the found HybridPetya installers. Observe that the installers we had been capable of acquire don’t take UEFI Safe Boot into consideration. Nonetheless, as defined within the CVE-2024-7344 exploitation part, there may be seemingly a variant with such an enchancment.

To resolve whether or not the system is UEFI primarily based, the installer retrieves the disk info (IOCTL_DISK_GET_DRIVE_LAYOUT_EX), checks whether or not the GPT partitioning scheme is used (PARTITION_STYLE_GPT), and walks via the partitions till it discovers the one with PARTITION_INFORMATION_GPT.PartitionType set to PARTITION_SYSTEM_GUID, which is the identifier of the EFI System Partition. After discovering the EFI System Partition, it continues:

• Eradicating the fallback UEFI bootloader, saved in EFIBootBootx64.efi.
• Dropping a disk-encryption-related configuration together with the encryption flag, to the EFIMicrosoftBootconfig file on the EFI System Partition; the encryption configuration comprises the Salsa20 encryption key, 8-byte nonce, and sufferer’s private set up key (base58-encoded information).
• Dropping an encryption-verification array consisting of 0x200 bytes with worth 0x07 to the EFIMicrosoftBootverify file on the EFI System Partition; this array is later encrypted by the bootkit element utilizing the identical Salsa20 key as used for disk encryption. The aim of this array is to confirm whether or not the sufferer entered a sound decryption key (by decrypting the array with the entered key, and verifying that the plaintext comprises an array of bytes with worth 0x07).
• Making a backup of EFIMicrosoftBootbootmgfw.efi, the default bootloader for Home windows-based programs, by copying it into EFIMicrosoftBootbootmgfw.efi.outdated.

When completed, it triggers a system crash (Blue Display Of Demise, BSOD) by utilizing the identical methodology that Petya did – invoking the NtRaiseHardError API with the ErrorStatus parameter set to 0xC0000350 (STATUS_HOST_DOWN) and the ResponseOption set to worth 6 (OptionShutdownSystem), leading to a system shutdown.

The abovementioned adjustments be sure that on programs with Home windows set as the first OS, the bootkit binary will likely be executed as soon as the machine is powered on once more.

CVE-2024-7344 exploitation

On this part, we study an archive that we found on VirusTotal that comprises a variant of the UEFI bootkit described within the UEFI bootkit part, however this time bundled in a specifically formatted cloak.dat file associated to CVE-2024-7344 – the UEFI Safe Boot bypass vulnerability that our crew publicly disclosed in early 2025.

An inventory of the information current within the archive together with their contents means that this EFI System Partition was copied from a system already encrypted by this Petya/NotPetya copycat variant. Observe that we haven’t obtained the installer answerable for deploying this model with the UEFI Safe Boot bypass, however primarily based on the archive’s contents, that are proven in Determine 11, it could be fairly just like the method described within the earlier part. Particularly, the archive comprises:

• EFIMicrosoftBootcounter, a file already containing a non-zero worth representing the variety of disk clusters beforehand encrypted by the bootkit,
• EFIMicrosoftBootconfig, a file with the encryption flag worth set to 1, that means that the disk needs to be already encrypted and the bootkit ought to proceed with displaying the ransom word,
• EFIMicrosoftBootbootmgfw.efi.outdated, a file with the primary 0x400 bytes XORed with the worth 0x07,
• EFIMicrosoftBootbootmgfw.efi, a authentic, however weak (CVE‑2024‑7344) UEFI utility signed by Microsoft (revoked in Microsoft’s dbx since January 2025); on this part we’ll discuss with this file with its unique identify reloader.efi, and
• EFIMicrosoftBootcloak.dat, a specifically crafted file loadable via reloader.efi and containing the XORed bootkit binary.

As described in our report from January 2025, the exploit mechanism is kind of easy. The cloak.dat file comprises specifically formatted information that comprises a UEFI utility. When the reloader.efi binary (deployed as bootmgfw.efi) is executed throughout boot, it searches for the presence of the cloak.dat file on the EFI System Partition, and hundreds the embedded UEFI utility from the file in a really unsafe manner, fully ignoring any integrity checks, thus bypassing UEFI Safe Boot.

Observe that our blogpost from January 2025 didn’t clarify the exploitation in positive element; thus, the malware creator most likely reconstructed the proper cloak.dat file format primarily based on reverse engineering the weak utility on their very own.

The vulnerability can’t be exploited on programs with Microsoft’s January 2025 dbx replace utilized. For steerage on the way to shield and confirm whether or not your system is uncovered to this vulnerability, test the Safety and Detection part of our January 2025 blogpost.

Conclusion

HybridPetya is now at the very least the fourth publicly identified instance of an actual or proof-of-concept UEFI bootkit with UEFI Safe Boot bypass performance, becoming a member of BlackLotus (exploiting CVE‑2022‑21894), BootKitty (exploiting LogoFail), and the Hyper-V Backdoor PoC (exploiting CVE‑2020‑26200). This exhibits that Safe Boot bypasses should not simply doable – they’re turning into extra frequent and enticing to each researchers and attackers.

Though HybridPetya shouldn’t be actively spreading, its technical capabilities – particularly MFT encryption, UEFI system compatibility, and Safe Boot bypass – make it noteworthy for future risk monitoring.

For any inquiries about our analysis revealed on WeLiveSecurity, please contact us at threatintel@eset.com.

ESET Analysis gives personal APT intelligence stories and information feeds. For any inquiries about this service, go to the ESET Risk Intelligence web page.

IoCs

A complete checklist of indicators of compromise (IoCs) and samples could be present in our GitHub repository.

Recordsdata

MITRE ATT&CK strategies

This desk was constructed utilizing model 17 of the MITRE ATT&CK framework.