Fake Claude AI Installer Campaign Distributes PlugX Malware via Phishing

Date: 2026-04-22
Tags: malware, malicious-tool

Executive Summary

Fake Claude AI installer mimicking Anthropic spreads PlugX malware on Windows, using DLL sideloading to gain persistent remote access to infected systems. Cybersecurity experts from Malwarebytes found a malicious campaign where scammers use the popularity of Anthropic's AI tool Claude to spread malware. Hackers made a fake website that looks just like the official one from Anthropic and offers a Pro version of the tool for Windows to lure people into downloading a malicious file.

Campaign Summary

Field	Detail
Campaign / Malware	Claude AI Pro Installer Phishing Campaign
Attribution	Unknown (Financially Motivated Threat Actor) (confidence: low)
Target	Windows users seeking Claude AI Pro software; development teams using Claude
Vector	Phishing emails linking to fake Anthropic website distributing trojanized Claude installer package
Status	active
First Observed	2026-04-05

Detailed Findings

The scam kicks in after the user is led to visit a site via phishing emails and downloads a folder named Claude-Pro-windows-x64.zip. There is an MSI installer inside it that places a shortcut called Claude AI.lnk on the desktop, which runs a VBScript when clicked. This script first launches the original Claude app to keep the user distracted and simultaneously installs the PlugX malware to allow hackers to remotely control the compromised device. Researchers observed attackers using Kingmailer on 28 March 2026 and switching to CampaignLark on 5 April 2026 to distribute phishing emails. A simple spelling mistake reveals the fake: hackers created a folder named 'Cluade' instead of Claude at C:\Program Files (x86)\Anthropic\Claude\Cluade.

MITRE ATT&CK Mapping

Technique	ID	Context
Phishing	T1566	Phishing emails directing users to fake Anthropic download site
Execution	T1204	User execution of malicious VBScript via desktop shortcut
DLL Sideloading	T1574.001	PlugX malware leverages DLL sideloading for persistence

IOCs

Domains

_No specific IOCs published; detection signatures recommended for PlugX family and associated infrastructure_

Full URL Paths

_No specific IOCs published; detection signatures recommended for PlugX family and associated infrastructure_

Splunk Format

_No IOCs available for Splunk query_

Package Indicators

Claude-Pro-windows-x64.zip

Detection Recommendations

Alert on downloads of Claude-Pro-windows-x64.zip or variants; monitor for installation of files to C:\Program Files (x86)\Anthropic\Claude\Cluade; detect PlugX malware signatures (NOVUpdate.exe, avk.dll in Startup folders); block Kingmailer and CampaignLark infrastructure IPs at email gateway; implement YARA rules for PlugX DLL sideloading patterns; educate users to download only from official claude.ai domain.

References

[Malwarebytes / Hackread] Fake Claude AI Installer Targets Windows Users with PlugX Malware (2026-04-15) — https://hackread.com/fake-claude-ai-installer-plugx-malware-windows-users/