Symantec researchers have discovered a custom backdoor, named Betruger, linked to affiliates of the RansomHub ransomware operation. Betruger is a versatile tool that combines several functionalities, including credential theft, keystroke logging, screenshot capture, privilege escalation, and network scanning. By integrating these multiple functions into a single tool, Betruger minimizes the need for additional malicious software, lowering the attack footprint and making detection more difficult during ransomware attacks.
Disguised as “mailer.exe” or “turbomailer.exe,” the Betruger backdoor appears legitimate but lacks any actual mailing functions. This deception is likely a strategy to avoid raising suspicions on compromised systems. Its design and purpose suggest it was developed specifically to support ransomware operations by simplifying and streamlining the tools needed to carry out attacks, thus increasing the efficiency of RansomHub’s affiliates.
RansomHub is a Ransomware-as-a-Service (RaaS) operation managed by the cybercrime group Greenbottle, which has rapidly gained prominence since its emergence in February 2024. By the third quarter of 2024, RansomHub became one of the most prolific ransomware operations in terms of the number of attacks. Greenbottle’s success stems partly from the group’s ability to offer affiliates better terms than rival operations, such as a higher percentage of ransom payments and a payment model where affiliates are paid by the victim first, ensuring greater financial incentives.
In addition to Betruger, affiliates of RansomHub use a wide range of tools and techniques to enhance their attacks. These include exploiting vulnerabilities like CVE-2022-24521 and CVE-2023-27532 to escalate privileges and disable security mechanisms. Tools such as Mimikatz, Impacket, and Stowaway Proxy, along with remote access tools like ScreenConnect and Splashtop, are commonly employed for data exfiltration and remote access. Betruger’s deployment in several RansomHub attacks highlights its growing use in the operation, as it aids in the streamlined execution of these attacks and further cements RansomHub’s position as a leading threat in the ransomware landscape.
