📂File Transfers

This scenario is a perfect example of how important it is for penetration testers and red teamers to understand multiple file transfer methods, and more importantly, how to adapt when common techniques are blocked.

Here’s a breakdown and summary of key lessons and techniques highlighted in your scenario:

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⚙️ Scenario Summary: File Transfer Challenges in a Hardened Environment

Initial Access:

• Gained Remote Code Execution (RCE) on an IIS web server via unrestricted file upload.

• Uploaded a web shell to get a reverse shell for further enumeration.

Privilege Escalation Attempt:

• Attempted to use PowerUp.ps1 via PowerShell ➡️ Blocked by App Control Policy.

• Discovered SeImpersonatePrivilege manually.

• Chose PrintSpoofer binary to escalate privileges.

File Transfer Hurdles:

Method Attempted	Result	Reason for Failure
PowerShell	❌ Blocked	App Control Policy
Certutil from GitHub	❌ Blocked	Web content filtering
FTP (port 21)	❌ Blocked	Firewall blocked outbound FTP
SMB (TCP 445) using smbserver.py	✅ Success	SMB allowed outbound

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🧠 Key Takeaways

1. Adaptability Is Critical:

   • You must pivot quickly to alternative transfer methods when blocked.

2. Common File Transfer Methods (Windows):

Method	Protocol/Tool	Notes
PowerShell Invoke-WebRequest / Invoke-Expression	HTTP	Powerful but often monitored
Certutil	HTTP	Common fallback, but may be disabled or filtered
bitsadmin	HTTP	Deprecated, but can be useful
Windows FTP Client	FTP	Needs port 21 open
smbserver.py (Impacket)	SMB	✅ Often succeeds if port 445 is open
Encoding (Base64 / Hex)	Clipboard / Echo	Good in restricted shells
DNS Tunneling	DNS	Rare but stealthy
Wget / Curl (Linux)	HTTP/HTTPS	May be blocked by firewall or proxy
Email / Cloud Upload	SMTP/HTTPS	Often blocked by DLP solutions

1. Network Awareness:

   • Firewalls, proxies, IDS/IPS, and web filters can all block or alert on your transfer attempts.

   • Outbound restrictions are common; inbound traffic (SMB pull) may work better.

2. Tools to Know:

   • smbserver.py (Impacket) – set up quick SMB shares
   • SimpleHTTPServer (Python) – easy local file hosting
   • ncat, scp, curl, wget, socat – all offer unique file transfer opportunities

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📌 Practical Tip: Use a File Transfer Checklist

Whenever you're stuck on a target:

1. Can I use PowerShell?

2. Is certutil available?

3. Are outbound ports like 80, 443, or 445 open?

4. Can I set up an SMB share with smbserver.py?

5. Can I encode a small binary as Base64 and reconstruct it?

6. Are there any mapped drives or local tools I can abuse?

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🎯 Final Thoughts

• File transfer is a foundational red team skill. This module trains you to think like an attacker in a constrained environment.

• Always have multiple options ready.

• Think like a defender too: if you were defending this system, how would you stop these transfers?

Would you like a cheat sheet of file transfer methods for restricted environments or an interactive exercise plan based on this scenario?