Fake Claude Website Distributes PlugX RAT

Summary

A malicious website impersonating Anthropic Claude distributed a remote access trojan (PlugX) through a fake installer. The attack chain used a VBScript dropper to execute a legitimate G DATA antivirus updater (NOVUpdate.exe) for DLL sideloading while installing the real Claude app in the foreground. The infection self-cleaned to hide artifacts, establishing C&C connections to Alibaba Cloud infrastructure.

Full text

A website posing as a legitimate Anthropic Claude domain was caught serving a remote access trojan to its visitors, Malwarebytes reports. Relying on Claude’s popularity, a threat actor created a site that hosts a download link pointing to a ZIP archive allegedly containing a pro version of the LLM. The file contains an MSI installer that mimics the legitimate Anthropic installation chain and installs the real Claude application. When the user attempts to launch the Claude app via the Desktop shortcut created during the installation, however, a VBScript dropper runs the real app in the foreground while installing malware in the background, Malwarebytes explains. The VBScript drops three files in the startup folder, including NOVUpdate.exe, a signed G DATA antivirus updater abused for DLL sideloading to execute a PlugX malware variant. PlugX is a known remote access trojan (RAT) that has been used in various espionage campaigns for nearly a decade.Advertisement. Scroll to continue reading. Within seconds after being dropped, NOVUpdate.exe creates a TCP connection to its command-and-control (C&C) infrastructure on Alibaba Cloud. In addition to dropping files in the startup folder, the initial VBScript writes a batch file to delete itself and the script, hiding evidence of infection. The sideloading files in the startup folder and the NOVUpdate.exe process are the only artifacts that persist on the infected system. “The script also wraps the entire malicious payload section in an On Error Resume Next statement, silently swallowing any errors so that failures in the deployment do not produce visible error dialogs that might alert the victim,” Malwarebytes notes. The infection chain was seen in February in a phishing campaign relying on fake meeting invitations to infect recipients with PlugX malware. As Malwarebytes notes, while PlugX has been historically associated with Chinese espionage groups, its source code has been shared among threat actors, making attribution difficult. “What is clear is that the operators behind this campaign have combined a proven sideloading technique with a timely social engineering lure—exploiting the surging popularity of AI tools to trick users into running a trojanized installer,” Malwarebytes notes. Related: Industry Reactions to Iran Hacking ICS in Critical Infrastructure: Feedback Friday Related: Russian APT Star Blizzard Adopts DarkSword iOS Exploit Kit Related: China-Linked Hackers Hit Asian Militaries in Patient Espionage Operation Related: Hacktivists, State Actors, Cybercriminals Target Global Defense Industry, Google Warns Written By Ionut Arghire Ionut Arghire is an international correspondent for SecurityWeek. 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Indicators of Compromise

• malware — PlugX
• malware — NOVUpdate.exe

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