Malware Initial Assessment: Remcos RAT Analysis

Remcos is a well-known Remote Access Trojan (RAT) used by cybercriminals to gain unauthorized access to victim systems. It allows attackers to execute commands, steal data, and maintain persistence. Below is a detailed analysis of Remcos RAT, including detection, analysis techniques, and countermeasures.

You Should Know: Practical Steps for Analyzing Remcos RAT

1. Detection & Initial Analysis

• Static Analysis with PEStudio:

  pestudio malware_sample.exe
  

  Check for suspicious imports (e.g., VirtualAllocEx, CreateRemoteThread), embedded resources, and anomalous strings.

• YARA Rule for Detection:

  rule Remcos_RAT {
  meta:
  description = "Detects Remcos RAT"
  author = "Your Name"
  strings:
  $s1 = "Remcos" nocase
  $s2 = "StartUp" wide
  $s3 = "WinExec" nocase
  condition:
  any of them
  }
  

2. Dynamic Analysis (Sandbox Execution)

• Monitor Process Behavior with ProcMon:

  Procmon.exe /AcceptEula /Quiet
  

  Filter for Process Create, File Write, and `Registry SetValue` events.

• Network Traffic Analysis (Wireshark):

  wireshark -k -i eth0 -Y "tcp.port == 443 || tcp.port == 80"
  

  Look for C2 (Command & Control) IPs communicating with the infected host.

3. Memory Forensics (Volatility)

• Extract Suspicious Processes:

  volatility -f memory_dump.raw pslist | grep -i "remcos"
  

• Dump Malicious DLLs:

  volatility -f memory_dump.raw dlldump -p <PID> -D output/
  

4. Persistence Mechanisms

• Check Registry for Auto-Start Entries:

  reg query "HKCU\Software\Microsoft\Windows\CurrentVersion\Run" /s
  

• Scheduled Tasks Analysis:

  schtasks /query /fo LIST /v
  

5. Removal & Mitigation

• Kill Malicious Process:

  taskkill /F /PID <Malicious_PID>
  

• Delete Malicious Files:

  del /F /Q "%APPDATA%\remcos.exe"
  

• Block C2 IPs via Firewall:

  netsh advfirewall firewall add rule name="Block_Remcos_C2" dir=out action=block remoteip=<C2_IP>
  

What Undercode Say

Remcos RAT remains a persistent threat due to its evasion techniques and modular capabilities. Security teams should:
– Regularly update YARA rules for detection.
– Monitor process injections (CreateRemoteThread).
– Use endpoint detection (EDR) for behavioral analysis.
– Educate users on phishing (common Remcos delivery method).

Expected Output:

• Detected Remcos process in memory dump.
• Identified C2 server: 185.xxx.xxx.xxx.
• Extracted malicious payload from %Temp%.
• Blocked C2 traffic via firewall rules.

Prediction

Remcos variants will increasingly use API unhooking and process hollowing to evade EDR solutions. Future versions may leverage legitimate cloud services for C2 communication.

(Relevant URLs if needed: MITRE ATT&CK Remcos)

References:

Reported By: Marc Ochsenmeier – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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