TChopper – Conduct Lateral Movement Attack By Leveraging Unfiltered Services Display Name To Smuggle Binaries As Chunks Into The Target Machine

New technique I have discovered recently and give it a nickname (Chop chop) to perform lateral movement using windows services display name and WMI by smuggling the malicious binary as base64 chunks and automate the process using the TChopper tool.

How it works

• the tool will get the file you willing to smuggle and encode the file as base64 into memory stream
• divide the length of each line to fit 150-250 character length (250 is maximum allowed space for service lpDisplayname parameter https://docs.microsoft.com/en-us/windows/win32/api/winsvc/nf-winsvc-createservicea).
• for chop chop attack it will create a unique service for each segmented chunk => start the service => then delete it to avoid duplicates or you can choose to only modify the service attack mode to be more faster and stable.
• later on, it will modify service lpbinarypath parameter with required command line to grab service display name and pip out the results into tmp_payload.txt
• finally, after finishing delivering all chuncks of the file as base64, the tool will create another service to decode the content into valid executbale and run it

while if you are conducting lateral movment using WMI technique you can also use Chopper to do that

• Tchopper will authenticate you session using WMI
• creation of multiple process and use powershell unique command to pip out each segment to c:userspublicchop.enc
• create final process to use certutil to decode the content into binary and execute it

Usage

#chop chop mode 
chopper.exe -s -u USERNAME -p PASSWORD -d DOMAIN -f BINARYLOCAL PATH 


# chop chop done 
chopper.exe -m -u USERNAME -p PASSWORD -d DOMAIN -f BINARYLOCAL PATH 

# use WMI to smuggle 
chopper.exe -w -u DOMAINUSERNAME -p PASSWORD -t MACHINE -f LOCALBINARYPATH

Detailed research

Smuggling via Windows services display name – Lateral movement