Fake Claude AI Site Delivers Beagle Backdoor via Malvertising

A malvertising and SEO-poisoning campaign is impersonating Anthropic’s Claude AI with the domain claude-pro[.]com, luring users to download a trojanized Windows installer that deploys a newly identified backdoor called Beagle. Researchers said the fake site appeared in sponsored search results and mimicked Claude branding to distribute a ZIP archive containing an MSI package that installed a legitimate signed G DATA executable alongside a malicious DLL, abusing DLL sideloading to begin the infection chain.

After execution, the malware decrypts additional payloads, launches DonutLoader, and loads Beagle entirely in memory to reduce disk-based detection. The backdoor provides remote access functions including command execution, file transfer, directory management, and self-uninstallation, and communicates with license[.]claude-pro[.]com over TCP 443 or UDP 8080 using a hardcoded AES key. Sophos X-Ops said the campaign has been active for months, uses anti-analysis measures and shared tooling such as a reused XOR key, and relies on infrastructure including Cloudflare and Alibaba Cloud; researchers also noted overlaps with activity linked to PlugX operators and related impersonation of vendors including Trellix, CrowdStrike, SentinelOne, and Microsoft Defender.