The Zola variant of Proton ransomware, identified by Acronis researchers in May 2024, introduces significant changes to the ransomware’s functionality. This variant includes new features like a keyboard layout-based kill switch that halts the attack if a Persian layout is detected. The Zola variant also includes a check for administrative privileges, which prompts the user to run the malware as an administrator if initial checks fail. The malware uses various common hacking tools, such as Mimikatz and ProcessHacker, and ensures that only one instance runs at a time by creating a mutex, a feature consistent across Proton variants.
Once the kill switch and privilege checks are bypassed, Zola proceeds to prepare the system for file encryption. The malware generates a unique victim ID and key information, deletes shadow copies, and modifies the boot configuration to prevent recovery. Additionally, it uses the vssadmin command to delete shadow copies and the BCDEdit tool to disable Windows’ automatic repair function, ensuring that the system fails to recover from boot issues. These measures make it harder for victims to restore their files and system after an attack.
Zola’s encryption methods differ from earlier Proton variants, as it switched from using elliptic-curve cryptography (ECC) and AES encryption to the ChaCha20 encryption scheme. Despite this change, the ransom note remains largely the same, claiming that AES and ECC were used for encryption, which is misleading. The malware encrypts files across various directories, including network-attached storage, and spawns threads to encrypt files simultaneously. It also tries to kill 137 processes and 79 services, including security software, to prevent interference during encryption.
In addition to its encryption efforts, Zola continues a feature introduced in earlier Proton variants that fills up a disk with uninitialized data. This process, which writes 500 KB chunks to the disk, serves to complicate forensic investigations and recovery efforts. The ransom note is placed in each encrypted folder, and the desktop wallpaper is changed to display the ransom instructions. This added disk-filling function is suspected to make it more difficult for researchers and victims to recover data or track the attacker’s actions after the encryption process is complete.
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