T1140: Deobfuscate/Decode Files or Information
Adversaries may use Obfuscated Files or Information to hide artifacts of an intrusion from analysis. They may require separate mechanisms to decode or deobfuscate that information depending on how they intend to use it. Methods for doing that include built-in functionality of malware or by using utilities present on the system.
One such example is the use of certutil to decode a remote access tool portable executable file that has been hidden inside a certificate file. Another example is using the Windows <code>copy /b</code> or <code>type</code> command to reassemble binary fragments into a malicious payload.
Sometimes a user's action may be required to open it for deobfuscation or decryption as part of User Execution. The user may also be required to input a password to open a password protected compressed/encrypted file that was provided by the adversary.
How it's found
Detect Adversary Deobfuscation or Decoding of Files and Payloads: An adversary leverages built-in tools such as certutil.exe, powershell.exe, or copy.exe to decode, reassemble, or extract hidden malicious content from obfuscated containers or encoded formats. The decoding utility often spawns shortly after file staging or download and may be chained with script interpreters or further payload execution. The adversary uses native utilities like base64, gzip, tar, or openssl to decode, decompress, or decrypt files that were previously staged or downloaded. These tools may be chained with curl/wget and executed via bash/zsh, often to extract an embedded payload or reverse shell script. The adversary invokes built-in scripting or decoding tools like base64, plutil, or AppleScript-based utilities to decode files embedded in staging artifacts. Decoding often occurs post-download or as part of post-exploitation payload deployment via zsh, python, or osascript.
Standards mapping
Where this fits in a TurboPentest engagement
This weakness is not covered by the automated black-box pentest. IntegSec pentesters cover it in a manual engagement.
Frequently asked questions
What is T1140 Deobfuscate/Decode Files or Information?
Adversaries may use Obfuscated Files or Information to hide artifacts of an intrusion from analysis. They may require separate mechanisms to decode or deobfuscate that information depending on how they intend to use it. Methods for doing that include built-in functionality of malware or by using utilities present on the system. One such example is the use of certutil to decode a remote access tool portable executable file that has been hidden inside a certificate file. Another example is using the Windows <code>copy /b</code> or <code>type</code> command to reassemble binary fragments into a malicious payload. Sometimes a user's action may be required to open it for deobfuscation or decryption as part of User Execution. The user may also be required to input a password to open a password protected compressed/encrypted file that was provided by the adversary.
Which tactics does T1140 belong to?
T1140 maps to the Stealth tactic.
Does TurboPentest test for Deobfuscate/Decode Files or Information?
This weakness is not covered by the automated black-box pentest. IntegSec pentesters cover it in a manual engagement.
Related MITRE ATT&CK techniques
About this reference
These security references are maintained by IntegSec, an offensive-security firm whose team holds CISSP, OSCP, and OSCE certifications and has run thousands of penetration tests. Content is kept current as tools, standards, and attack techniques evolve.
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