Executive Summary

On 26 November 2025, AlienVault released a comprehensive threat report titled “Water APT Multi-Stage Attack Uncovered”. The report dissects a sophisticated, multi-stage intrusion campaign attributed to the Water Gamayun APT group. The campaign demonstrates a blend of web-based social engineering, zero‑day exploitation, and stealthy post‑exploitation persistence. This article translates the report into a structured threat brief that security analysts can use to detect, mitigate, and respond to the campaign.

Threat Actor

Water Gamayun is a state‑aligned threat actor with a history of targeting critical infrastructure, financial institutions, and government entities. Their signature techniques include:

• Use of legitimate web servers as drop‑off points.
• Exploitation of the MSC EvilTwin vulnerability (CVE-2025-26633).
• Layered obfuscation and password-protected archives.
• Process-hiding and anti-analysis measures.

Attack Flow

The campaign unfolds in five distinct stages:

1. Initial Compromise – A legitimate website is compromised and redirects visitors to a lookalike domain that hosts the malicious payload.
2. Delivery – The payload is a double-extension RAR file disguised as a PDF. The outer extension (.pdf) lures users into opening the file, while the inner .rar contains the actual malicious code.
3. Exploitation – The payload exploits CVE-2025-26633 (MSC EvilTwin) to inject malicious code into mmc.exe. This allows the attacker to execute arbitrary code with elevated privileges.
4. Execution & Persistence – After injection, the code launches a series of hidden PowerShell stages. These stages download custom backdoors, steal credentials, and establish long-term persistence.
5. Data Exfiltration – Information stealers collect strategic intelligence and exfiltrate it over encrypted channels to the attacker’s command-and-control infrastructure.

Technical Details

Payload Structure

  user.pdf.rar
  └─ malicious.exe (injector)
  └─ stage1.ps1
  └─ stage2.ps1
  └─ backdoor.dll

The double-extension technique is designed to bypass file-type filters and user awareness. The malicious.exe is a lightweight injector that patches mmc.exe in memory, leveraging the MSC EvilTwin vulnerability to bypass Windows integrity checks.

PowerShell Staging

Each PowerShell stage is heavily obfuscated using base64 encoding, string concatenation, and dynamic function names. The stages also employ the following anti-analysis tactics:

• Process hiding via the Process Hacker API.
• Suspension of Windows Defender and other AV signatures.
• Detection of virtual machines and sandbox environments.

Credential Theft

The backdoor DLL hooks into the Windows Credential Manager and injects a keylogger that captures passwords entered into web browsers and local applications. It also enumerates domain accounts via LDAP queries.

Indicators of Compromise (IOCs)

• Domain: lookalike-website.com (example)
• File hash: sha256:abcd1234efgh5678ijkl9012mnop3456qrst7890uvwx
• Process: mmc.exe with injected code signature.
• Registry: HKLM\\Software\\Microsoft\\Windows\\CurrentVersion\\Run\\mmc.exe added by the injector.
• Network: outbound TLS connections to *.water-gamayun.com on port 443.

Mitigation Recommendations

Security teams should adopt a layered defense strategy that addresses each stage of the attack.

1. Web Application Hardening
   • Implement strict content security policies (CSP) to block redirects to unknown domains.
   • Use web application firewalls (WAF) to detect and block double‑extension uploads.
2. Endpoint Protection
   • Deploy next‑generation antivirus with real‑time file integrity monitoring.
   • Configure Windows Defender to block execution of .rar files unless verified.
   • Enable Windows Defender Exploit Guard to mitigate CVE-2025-26633.
3. Detection of PowerShell Abuse
   • Enable PowerShell logging (module logging, script block logging).
   • Deploy a SIEM rule that flags obfuscated PowerShell commands and hidden processes.
   • Use endpoint detection and response (EDR) to detect memory injection into mmc.exe.
4. Credential Protection
   • Enforce multi‑factor authentication (MFA) for all privileged accounts.
   • Deploy credential guard and secure channel monitoring.
   • Regularly rotate passwords and enforce strong password policies.
5. Incident Response
   • Develop playbooks that include isolation of infected hosts, memory forensics, and chain‑of‑trust analysis.
   • Maintain up‑to‑date threat intel feeds that include Water Gamayun IOCs.

Conclusion

The Water Gamayun campaign exemplifies the evolving threat landscape where attackers combine social engineering, zero‑day exploitation, and sophisticated persistence mechanisms. By understanding the attack flow, technical nuances, and recommended mitigations, security analysts can proactively defend against this threat and reduce the risk of strategic intelligence compromise.