Cisco Talos, in collaboration with the Dutch police, has successfully obtained a decryption tool for the Tortilla variant of the Babuk ransomware, leading to the arrest of the ransomware’s operator in Amsterdam. Tortilla, a Babuk ransomware spin-off, specifically targeted Microsoft Exchange servers using ProxyShell exploits to deploy the data-encrypting malware. Although Avast had previously released a decryptor for Babuk, it was ineffective against Tortilla encryption due to the use of a different private key. Cisco Talos shared threat intelligence, enabling authorities to identify and apprehend the threat actor, while Avast incorporated the Tortilla decryption key into its Babuk decryptor.
The Tortilla ransomware variant emerged shortly after the source code of the original Babuk ransomware leaked on a hacker forum. This new variant posed challenges for decryption, as it utilized a distinct private key for encryption. The decryptor obtained by Cisco Talos and Dutch law enforcement was the one provided by the ransomware operator to victims who paid the ransom. This breakthrough allowed the researchers to extract a single public/private key pair used in all Tortilla attacks, which they subsequently shared with Avast to enhance their existing Babuk decryptor.
Victims affected by the Tortilla variant of Babuk ransomware can now download Avast’s updated decryption tool for free, providing a means to recover their encrypted data. Cisco Talos emphasized that Tortilla is not an isolated incident, as several other operations, including Rook, Night Sky, Pandora, and others, have emerged since December 2021, using Babuk ransomware code to encrypt victims. The successful collaboration between security researchers and law enforcement highlights the importance of public-private partnerships in combating cyber threats and providing effective solutions for victims of ransomware attacks.