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UNC6384 Targets Diplomats with PlugX via Captive Portal Hijacks

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2 unique sources, 3 articles

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UNC6384, a China-nexus threat actor, has been targeting diplomats in Southeast Asia and other entities globally to advance Beijing's strategic interests. The group employs a multi-stage attack chain leveraging advanced social engineering, valid code signing certificates, adversary-in-the-middle (AitM) attacks, and indirect execution techniques to evade detection. The campaign, detected in March 2025, uses captive portal redirections to deliver a PlugX variant called SOGU.SEC. The attacks involve redirecting web traffic through a captive portal to a threat actor-controlled website, downloading a digitally signed downloader (STATICPLUGIN), and deploying the SOGU.SEC backdoor in memory. The malware supports commands to exfiltrate files, log keystrokes, and launch remote command shells. The campaign highlights the sophistication of PRC-nexus threat actors and their evolving operational capabilities. The campaign targeted around two dozen victims, primarily Southeast Asian diplomats, between March and July 2025. The attack chain involved compromised edge devices intercepting captive portal checks and redirecting users to a malicious website. The malicious website used a valid TLS/SSL certificate issued by Let's Encrypt to avoid browser security warnings. The first-stage malware, STATICPLUGIN, dropped a launcher called CANONSTAGER, which used unconventional techniques to hide its activities. The final payload was a variant of the PlugX backdoor, tracked by Google as SOGU.SEC. In September 2025, new information revealed that the PlugX variant overlaps with RainyDay and Turian backdoors, targeting telecommunications and manufacturing sectors in Central and South Asia. The campaign is linked to Mustang Panda, which also uses Bookworm malware. Bookworm has been used since 2015 and includes capabilities to execute commands, upload/download files, exfiltrate data, and establish persistent access.

Timeline

  1. 27.09.2025 15:06 1 articles · 6d ago

    PlugX Variant Linked to Mustang Panda and Bookworm Malware

    The new PlugX variant overlaps with RainyDay and Turian backdoors in its use of legitimate applications for DLL side-loading, encryption/decryption algorithms, and RC4 keys. The PlugX variant uses a configuration structure similar to RainyDay, associated with Lotus Panda (Naikon APT). The campaign targets telecommunications and manufacturing sectors in Central and South Asia. The attack chains involve abusing a legitimate executable associated with Mobile Popup Application to sideload a malicious DLL for payload execution. The PlugX variant includes an embedded keylogger plugin. The campaign is linked to Mustang Panda, which also uses Bookworm malware. Bookworm malware has been used since 2015 and includes capabilities to execute commands, upload/download files, exfiltrate data, and establish persistent access. Bookworm utilizes legitimate-looking domains or compromised infrastructure for C2 purposes. Bookworm variants share overlaps with TONESHELL, another backdoor associated with Mustang Panda. Bookworm employs a modular architecture that makes static analysis challenging.

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  2. 25.08.2025 21:11 3 articles · 1mo ago

    UNC6384 Deploys PlugX via Captive Portal Hijacks Targeting Diplomats

    The campaign targeted around two dozen victims, primarily Southeast Asian diplomats, between March and July 2025. The attack chain involved compromised edge devices intercepting captive portal checks and redirecting users to a malicious website. The malicious website used a valid TLS/SSL certificate issued by Let's Encrypt to avoid browser security warnings. The first-stage malware, STATICPLUGIN, dropped a launcher called CANONSTAGER, which used unconventional techniques to hide its activities. The final payload was a variant of the PlugX backdoor, tracked by Google as SOGU.SEC. The new PlugX variant overlaps with RainyDay and Turian backdoors, targeting telecommunications and manufacturing sectors in Central and South Asia. The campaign is linked to Mustang Panda, which also uses Bookworm malware.

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