Adversaries may execute their own payloads by placing a malicious dynamic library (dylib) with an expected name in a path a victim application searches at runtime. The dynamic loader will try to find the dylibs based on the sequential order of the search paths. Paths to dylibs may be prefixed with <code>@rpath</code>, which allows developers to use relative paths to specify an array of search paths used at runtime based on the location of the executable.  Additionally, if weak linking is used, such as the <code>LC_LOAD_WEAK_DYLIB</code> function, an application will still execute even if an expected dylib is not present. Weak linking enables developers to run an application on multiple macOS versions as new APIs are added.

Adversaries may gain execution by inserting malicious dylibs with the name of the missing dylib in the identified path.(Citation: Wardle Dylib Hijack Vulnerable Apps)(Citation: Wardle Dylib Hijacking OSX 2015)(Citation: Github EmpireProject HijackScanner)(Citation: Github EmpireProject CreateHijacker Dylib) Dylibs are loaded into an application's address space allowing the malicious dylib to inherit the application's privilege level and resources. Based on the application, this could result in privilege escalation and uninhibited network access. This method may also evade detection from security products since the execution is masked under a legitimate process.(Citation: Writing Bad Malware for OSX)(Citation: wardle artofmalware volume1)(Citation: MalwareUnicorn macOS Dylib Injection MachO)
Dylib Hijacking
source_name: mitre-attack  url: https://attack.mitre.org/techniques/T1574/004  external_id: T1574.004     source_name: MalwareUnicorn macOS Dylib Injection MachO  description: Amanda Rousseau. (2020, April 4). MacOS Dylib Injection Workshop. Retrieved March 29, 2021.  url: https://malwareunicorn.org/workshops/macos_dylib_injection.html#5     source_name: Apple Developer Doco Archive Run-Path  description: Apple Inc.. (2012, July 7). Run-Path Dependent Libraries. Retrieved March 31, 2021.  url: https://developer.apple.com/library/archive/documentation/DeveloperTools/Conceptual/DynamicLibraries/100-Articles/RunpathDependentLibraries.html     source_name: Wardle Dylib Hijacking OSX 2015  description: Patrick Wardle. (2015, March 1). Dylib Hijacking on OS X. Retrieved March 29, 2021.  url: https://www.virusbulletin.com/uploads/pdf/magazine/2015/vb201503-dylib-hijacking.pdf     source_name: Writing Bad Malware for OSX  description: Patrick Wardle. (2015). Writing Bad @$$ Malware for OS X. Retrieved July 10, 2017.  url: https://www.blackhat.com/docs/us-15/materials/us-15-Wardle-Writing-Bad-A-Malware-For-OS-X.pdf     source_name: Wardle Dylib Hijack Vulnerable Apps  description: Patrick Wardle. (2019, July 2). Getting Root with Benign AppStore Apps. Retrieved March 31, 2021.  url: https://objective-see.com/blog/blog_0x46.html     source_name: wardle artofmalware volume1  description: Patrick Wardle. (2020, August 5). The Art of Mac Malware Volume 0x1: Analysis. Retrieved March 19, 2021.  url: https://taomm.org/vol1/pdfs.html     source_name: Github EmpireProject HijackScanner  description: Wardle, P., Ross, C. (2017, September 21). Empire Project Dylib Hijack Vulnerability Scanner. Retrieved April 1, 2021.  url: https://github.com/EmpireProject/Empire/blob/master/lib/modules/python/situational_awareness/host/osx/HijackScanner.py     source_name: Github EmpireProject CreateHijacker Dylib  description: Wardle, P., Ross, C. (2018, April 8). EmpireProject Create Dylib Hijacker. Retrieved April 1, 2021.  url: https://github.com/EmpireProject/Empire/blob/08cbd274bef78243d7a8ed6443b8364acd1fc48b/lib/modules/python/persistence/osx/CreateHijacker.py     