Astaroth Malware Abuses Ngrok and Steganography for C2

Summary

Astaroth, also known as Guildma, is a Delphi-based Windows banking trojan that targets financial and cryptocurrency portals. It utilizes multi-stage loading, process hollowing, and in-memory injection to evade detection. The malware maintains resilience by fetching encrypted configurations via steganographic images and routing C2 traffic through Ngrok tunnels.

Investigation

The report details the execution flow of Astaroth from initial phishing delivery through credential theft. It highlights the malware’s advanced anti-analysis techniques, including process enumeration, volume serial number fingerprinting, and locale-based sandbox detection. The investigation also exposes its use of custom binary protocols and steganography for C2 resilience.

Mitigation

Security teams should implement robust email filtering to block malicious LNK, VBS, and HTA files. Monitoring for unauthorized use of Ngrok tunnels and suspicious process injection into RegSvcs.exe is critical. Additionally, validating security controls against known banking trojan TTPs can help identify evasion attempts.

Response

Upon detection, isolate affected systems to prevent credential exfiltration via Ngrok. Conduct forensic analysis of memory and local files like dump.log to identify the C2 configuration. Perform a comprehensive password reset for all banking and cryptocurrency accounts accessed on the compromised machine.

Simulation Execution

Prerequisite: The Telemetry & Baseline Pre-flight Check must have passed.

Rationale: This section details the precise execution of the adversary technique (TTP) designed to trigger the detection rule. The commands and narrative MUST directly reflect the TTPs identified and aim to generate the exact telemetry expected by the detection logic. Abstract or unrelated examples will lead to misdiagnosis.

• Attack Narrative & Commands: The adversary intends to establish a Command and Control (C2) channel using the Astaroth malware’s preferred method: Ngrok tunneling. By using the specific subdomain 5.tcp.ngrok.io, the attacker aims to bypass simple IP blacklists. The simulation will mimic this by initiating a TCP connection to the target subdomain. This action is designed to trigger the network connection log entry specifically looking for the 5.tcp.ngrok.io domain in the destination field.

• Regression Test Script:

  # Simulation of Astaroth C2 via Ngrok subdomain
  # Note: This script only attempts a connection to trigger telemetry.
  $C2_Domain = "5.tcp.ngrok.io"
  $Port = 443 
  
  Write-Host "[!] Starting Astaroth C2 Simulation..."
  try {
      $connection = New-Object System.Net.Sockets.TcpClient
      $connection.Connect($C2_Domain, $Port)
      Write-Host "[+] Connection successful. Telemetry generated."
      $connection.Close()
  } catch {
      Write-Host "[-] Connection failed (expected if subdomain is inactive), but telemetry should still be generated."
  }

• Cleanup Commands:

  # No persistent changes made by simulation script.
  Write-Host "[*] Simulation cleanup complete. No artifacts remaining."