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xHunt Campaign: New PowerShell Backdoor Blocked Through DNS Tunnel Detection
xHunt's new CASHY200 PowerShell backdoor used DNS tunneling for C2; DNS security blocked beaconing at a Kuwait organization in September 2019.
Unit 42 describes CASHY200, a new PowerShell-based backdoor tied to the xHunt campaign that communicates with its C2 server windows64x[.]com via DNS tunneling, parsing commands from DNS answers. In September 2019, a Kuwait-based organization's DNS security service blocked the beaconing minutes after detection, cutting off adversary access. Samples dating to May and June 2018 and open source collection suggest the tool was used against Kuwait government organizations from spring 2018 through 2019, with malicious Word documents observed installing CASHY200 payloads configured with C2 domains such as firewallsupports[.]com and winx64-microsoft[.]com. The tool's name derives from identifiers stored under the registry key HKCU\Software\Microsoft\Cashe and the command value 200.
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Threat Brief: 3CXDesktopApp Supply Chain Attack (Updated)
Trojanized 3CXDesktopApp installers for Windows and macOS loaded RC4-encrypted shellcode delivering a backdoor to hundreds of thousands of 3CX users.
Threat actors compromised the 3CXDesktopApp build process, adding malicious libraries (ffmpeg.dll, d3dcompiler_47.dll) to installers downloaded from the developer's website. The Windows MSI loader decrypts embedded shellcode with RC4, sleeps for a random 1-4 weeks, then beacons to C2 hidden in icon files on GitHub. Unit 42 fingerprinted 247,277 IPs across 199 countries using 3CX applications and blocked shellcode execution at 127 Cortex XDR customers between March 9-30, 2023.
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TuxBot v3: Inside an IoT Botnet Framework With LLM
Unit 42 uncovers TuxBot v3, an LLM-assisted IoT botnet framework with 17-architecture builds, Telnet brute-forcing, and DDoS capabilities.
Palo Alto Unit 42 identified TuxBot v3 Evolution, a modular IoT botnet framework derived from AISURU, Wuhan-lineage botnets, and MHDDoS. The C-based bot brute-forces Telnet with 1,496 credential pairs, targets over 30 IoT device families, and communicates with a Go-based C2 over encrypted TCP with multiple fallback mechanisms including DGA, P2P, and DNS TXT. LLM-assisted development left hallucinated crypto implementations and broken exploit modules in the analyzed samples, though roughly 70% of core functionality works. Researchers warn polished production builds likely exist, raising the threat potential.
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Bisonal Malware Used in Attacks Against Russia and South Korea
Unit 42 details a Bisonal malware variant, active since 2014, targeting Russian and South Korean defense organizations via PDF-disguised spearphishing emails.
In early May, Unit 42 discovered a campaign delivering a Bisonal malware variant against at least one Russian communications security and cryptography company and one unidentified organization in South Korea. The variant, in the wild since at least 2014, introduces a new C2 cipher and rewritten networking and persistence code, with only 14 samples collected to date. Attackers spoofed Russian state corporation Rostec in spearphishing emails carrying an executable disguised with a PDF icon; the dropper decrypts an RC4-encrypted DLL and establishes persistence via a registry Run key. Bisonal has been used since 2013 against government, military, and defense targets in South Korea, Russia, Japan, and India, alongside successors Bioazih and Dexbia.
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