Ragnarök: F6 Investigates VantaCore Ransomware Attacks and Suspected Thor Rebrand
Specialists from F6’s Laboratory of Digital Forensics and Malware Research have reported a new threat to Russian businesses. In August 2026 the laboratory detected activity from a ransomware group calling itself VantaCore. The confirmed number of victims stands at no fewer than seven, with ransom demands reaching millions of dollars.
Researchers believe VantaCore is a rebrand of the previously known pro-Ukrainian group Thor. F6 has previously documented consolidation and regrouping among pro-Ukrainian collectives during 2025–2026. A parallel trend is the abandonment of LockBit 3 Black and Babuk in favor of custom encryptors. In March 2026 F6 reported that Bearlyfy had switched to its own GenieLocker ransomware; in August the same pattern appeared with VantaCore.
Reasons for dropping LockBit 3 Black and Babuk include their Russian origins and accumulated technical shortcomings. Nevertheless, the new encryptors retain code and design similarities with both families. VantaCore also launched a data-leak site in June 2026 and positioned itself as a professional Ransomware-as-a-Service operation, complete with a Tor chat for victim negotiations.
The group employs double and triple extortion. After encryption, stolen data is sold or published on its leak site and later reused for further attacks against Russian entities. Initial access vectors include poorly secured RDP and VPN services, vulnerabilities in public-facing applications, and compromised partner credentials.
Once inside the network, operators move laterally using harvested legitimate accounts over SMB and RDP. They perform reconnaissance with both custom scanners and native utilities such as ping, netsh, quser, qwinsta and net user. Persistence is achieved through newly created Windows services, while remote access is provided by the legitimate Tactical RMM tool and the custom VantaCoreRAT backdoor written in Go.
To remain undetected, the attackers obfuscate binaries, delete tools and logs after use, clear Windows event logs with PowerShell and wevtutil, and disable security products manually or via the SnowKiller BYOVD utility. Backups are destroyed by overwriting RAID arrays with arbitrary data using the open-source Bootice utility.
Encryption is performed by the custom VantaCore ransomware developed in C++. The binary accepts a hardcoded password on the command line and uses ChaCha20 with X25519 for file encryption. Mass deployment is handled by the custom VantaCoreLoader tool, which spreads via administrative shares in a manner similar to LockBit 3 Black’s psexec_netspread module.
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