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