YARA-X's new macho module simplifies detecting patterns in Mach-O binaries compared to the manual byte-matching required in original YARA. The post walks through using macho.symtab, macho.imports, macho.exports, rpaths, dylibs, and entitlements, along with helper functions like has_import(), has_export(), has_rpath(), has_dylib(), and has_entitlement(). It also explains the deduplicated, sorted, lowercased MD5 hashing scheme used for hash-based detections across these structures, pointing readers to the full documentation for more detail.
Table of contents
Importing the macho moduleMyriad structures inside a Mach-O binaryBinary SimilarityQuestions this post answers
How do I detect a specific dylib or import in a Mach-O binary using YARA-X?
Use the macho module's has_dylib() function to check for a specific shared library loaded via a load command, or has_import() to check for a specific imported symbol. The macho module also exposes arrays like macho.imports and dylib structures that can be iterated directly in a YARA-X rule for more granular matching. Developers building malware detection rules can find deep dives like this through daily.dev's tech feeds.
How does YARA-X hash a list of entitlements or dylibs for detection purposes?
YARA-X computes an MD5 hash of the deduplicated, sorted, and lowercased entries joined by commas, such as md5("dylib_1,dylib_2,dylib_n"). This applies to categories like dylibs, imports, exports, and entitlements, allowing analysts to fingerprint a specific combination of Mach-O binary features with a single hash comparison. Security engineers comparing binary analysis techniques can track tooling changes like this via daily.dev.