Cyber Security Threat Summary:
“A relatively new ransomware operation calling itself Buhti appears to be eschewing developing its own payload and is instead utilizing variants of the leaked LockBit and Babuk ransomware families to attack Windows and Linux systems. While the group doesn’t develop its own ransomware, it does utilize what appears to be one custom-developed tool, an information stealer designed to search for and archive specified file types. Buhti, which first came to public attention in February 2023, was initially reported to be attacking Linux computers. However, Symantec’s Threat Hunter Team has also uncovered attempts to attack Windows computers on compromised networks. The group appears to be quick to exploit recently disclosed vulnerabilities, with one recent attack exploiting the recently patched PaperCut vulnerability. Since Buhti hasn’t been linked to any known cyber-crime group, Symantec has assigned the actor name Blacktail to its operators” (Symantec, 2023).

“Recent Buhti attacks exploited a recently discovered vulnerability in PaperCut NG and MF (CVE-2023-27350). The exploit allows an attacker to bypass authentication and remotely execute code. The vulnerability was disclosed and patched by PaperCut on March 15, 2023, and in recent weeks multiple threat actors have begun utilizing the exploit against unpatched systems. The attackers exploited the vulnerability in order to install Cobalt Strike, Meterpreter, Sliver, AnyDesk, and ConnectWise. The tools were leveraged to steal data from, and deliver the ransomware payload to, multiple computers on the targeted network. Blacktail appears quick to utilise new exploits. In February, they were reported to be exploiting a vulnerability in IBM’s Aspera Faspex file-exchange application (CVE-2022-47986)” (Symantec, 2023).

Security Officer Comments:
Analysis of the payload revealed that it was a minimally modified version of the leaked LockBit 3.0 (aka LockBit Black) ransomware. The ransomware includes a feature that drops a LockBit-branded .bmp file and makes it the Windows wallpaper, but this functionality was disabled by the attackers. The ransomware also has the capability to send system information about the infected computer to a command-and-control (C&C) server, but this functionality is also disabled and no C&C server is specified. LockBit 3.0 was developed for the Syrphid cyber-crime group (aka Bitwise Spider), which is the operator of the LockBit ransomware. The builder for the ransomware was leaked in September 2022, allegedly by a disgruntled developer.

Suggested Correction(s):
Backup your data, system images, and configurations, regularly test them, and keep the backups offline: Ensure that backups are regularly tested and that they are not connected to the business network, as many ransomware variants try to find and encrypt or delete accessible backups. Maintaining current backups offline is critical because if your network data is encrypted with ransomware, your organization can restore systems.

Update and patch systems promptly: This includes maintaining the security of operating systems, applications, and firmware in a timely manner. Consider using a centralized patch management system; use a risk- based assessment strategy to drive your patch management program.

Test your incident response plan: There's nothing that shows the gaps in plans more than testing them. Run through some core questions and use those to build an incident response plan: Are you able to sustain business operations without access to certain systems? For how long? Would you turn off your manufacturing operations if business systems such as billing were offline?

Check Your Security Team's Work: Use a 3rd party pen tester to test the security of your systems and your ability to defend against a sophisticated attack. Many ransomware criminals are aggressive and sophisticated and will find the equivalent of unlocked doors.

Segment your networks: There's been a recent shift in ransomware attacks – from stealing data to disrupting operations. It's critically important that your corporate business functions and manufacturing/production operations are separated and that you carefully filter and limit internet access to operational networks, identify links between these networks and develop workarounds or manual controls to ensure ICS networks can be isolated and continue operating if your corporate network is compromised. Regularly test contingency plans such as manual controls so that safety critical functions can be maintained during a cyber incident.

Train employees: Email remains the most vulnerable attack vector for organizations. Users should be trained how to avoid and spot phishing emails. Multi Factor authentication can help prevent malicious access to sensitive services.

Link(s):
https://symantec-enterprise-blogs.security.com/blogs/threat-intelligence/buhti-ransomware