Russian BlueAlpha APT Abuses Cloudflare Tunnels To Deliver Custom Malware

The state-sponsored cyber threat group BlueAlpha, linked to Russia’s Federal Security Service (FSB), has been actively targeting organizations with advanced cyber tactics since 2014. Recently, BlueAlpha has adopted a novel strategy by leveraging Cloudflare Tunnels to stage and deliver its GammaDrop malware, enhancing its ability to evade detection.

BlueAlpha employs spear phishing campaigns to distribute malicious HTML smuggling files embedded with JavaScript. These files execute custom malware variants GammaDrop and GammaLoad, enabling data exfiltration, credential theft, and persistent network access. The group’s updated approach involves:

• HTML Smuggling: Embedding JavaScript into HTML attachments to bypass traditional email security systems.
• Cloudflare Tunnels: Using the TryCloudflare tool to create subdomains for staging GammaDrop. This tactic hides malicious infrastructure behind Cloudflare’s network, complicating traditional detection.
• DNS Fast-Fluxing: Changing DNS records rapidly for its command-and-control (C2) servers, making it harder to trace.

The malware suite utilized by BlueAlpha includes:

• GammaDrop: A dropper ensuring the delivery and persistence of GammaLoad.
• GammaLoad: A custom VBScript capable of beaconing to C2 servers, deploying additional malware, and stealing sensitive data.

Mitigation Strategies:

1. Deploy tools to detect and block HTML smuggling activities, flagging suspicious JavaScript events like “onerror.”
2. Establish application control rules to block the execution of malicious .lnk files and untrusted executables, such as mshta.exe.
3. Monitor and restrict unauthorized DNS-over-HTTPS (DoH) traffic, especially queries targeting trycloudflare.com subdomains.

Organizations must invest in advanced detection and response capabilities to counteract sophisticated threats posed by BlueAlpha and similar state-sponsored groups. The group’s persistent use of obfuscation tactics and infrastructure hiding underscores the importance of continuous monitoring and proactive cybersecurity measures.