Obfuscated Files or Information: Stripped Payloads

Adversaries may attempt to make a payload difficult to analyze by removing symbols, strings, and other human readable information. Scripts and executables may contain variables names and other strings that help developers document code functionality. Symbols are often created by an operating system’s linker when executable payloads are compiled. Reverse engineers use these symbols and strings to analyze code and to identify functionality in payloads.[1][2]

Adversaries may use stripped payloads in order to make malware analysis more difficult. For example, compilers and other tools may provide features to remove or obfuscate strings and symbols. Adversaries have also used stripped payload formats, such as run-only AppleScripts, a compiled and stripped version of AppleScript, to evade detection and analysis. The lack of human-readable information may directly hinder detection and analysis of payloads.[3]

ID: T1027.008
Sub-technique of:  T1027
Tactic: Defense Evasion
Platforms: Linux, Windows, macOS
Version: 1.0
Created: 29 September 2022
Last Modified: 20 October 2022

Procedure Examples

ID Name Description
S1048 macOS.OSAMiner

macOS.OSAMiner has used run-only Applescripts, a compiled and stripped version of AppleScript, to remove human readable indicators to evade detection.[3]

Mitigations

This type of attack technique cannot be easily mitigated with preventive controls since it is based on the abuse of system features.

Detection

ID Data Source Data Component Detects
DS0022 File File Metadata

Detecting the presence of stripped payloads may be difficult and unwarranted in real-time, though analyzing contextual data about files (such as content and character entropy) may highlight attempts at obfuscation.

References