Detect Dylib Hijacking in Splunk
Adversaries on macOS may execute malicious payloads by placing a malicious dynamic library (dylib) in a path that a victim application searches at runtime. The macOS dynamic linker searches paths in order: @rpath (relative run-path), @loader_path, @executable_path, and standard system paths (/usr/lib, /System/Library). If an application references a dylib with a weak link (LC_LOAD_WEAK_DYLIB) and the dylib does not exist, an adversary can plant a malicious dylib with the correct name at the expected path. The Empire post-exploitation framework includes modules specifically for scanning and exploiting dylib hijacking vulnerabilities.
MITRE ATT&CK
- Technique
- T1574 Hijack Execution Flow
- Sub-technique
- T1574.004 Dylib Hijacking
- Canonical reference
- https://attack.mitre.org/techniques/T1574/004/
SPL Detection Query
index=osquery OR index=jamf OR index=mac_management sourcetype=osquery:file_events
| where path like "%.dylib"
| where path like "/tmp/%" OR path like "/var/folders/%" OR path like "/Users/%Library/%" OR path like "/private/tmp/%"
| eval SuspiciousPath=1
| table _time, host, path, action, sha256, pid, process_name
| sort - _time
```
ALTERNATIVE for Sysmon (macOS):
```
index=mac_os sourcetype="osquery:file_events" action=CREATED
| where match(path, "\.dylib$")
| where match(path, "(/tmp/|/var/folders/|/Users/.+/Library/)")
| eval RpathHijack=if(match(path, "@rpath"), 1, 0)
| table _time, host, path, sha256, process_name, pid
| sort - _timeDetects dylib creation in user-accessible macOS paths using osquery file integrity monitoring or macOS endpoint telemetry. Focuses on /tmp, /var/folders (user temp), and user Library paths where dylib hijacking payloads are most commonly staged. Suitable for environments using osquery, Jamf, or similar macOS management tools for security telemetry.
Data Sources
Required Sourcetypes
False Positives & Tuning
- Package managers (Homebrew, MacPorts) creating dylibs during installation
- Xcode and development tools creating dylibs during build processes
- macOS system update mechanisms staging libraries
- Third-party software installers creating application-specific dylibs
Other platforms for T1574.004
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1List Vulnerable Applications Using otool
Expected signal: Process creation event for otool. No file creation events generated. This is a read-only reconnaissance action. macOS audit logs (if enabled) would show the file read operations.
- Test 2Create Malicious Dylib in @rpath Location
Expected signal: File creation event for .dylib file in user Library path. Process creation events for gcc (if installed). The dylib file will appear as unsigned in code signing checks (codesign -v ~/Library/test-hijack/libtest.dylib).
- Test 3Verify DYLD Environment Variable Propagation
Expected signal: Process creation event for ls with DYLD_PRINT_LIBRARIES environment variable set. The output shows which dylibs ls loads. macOS SIP (System Integrity Protection) may suppress DYLD_* variables for protected binaries.
References (6)
- https://attack.mitre.org/techniques/T1574/004/
- https://objective-see.com/blog/blog_0x46.html
- https://www.virusbulletin.com/uploads/pdf/magazine/2015/vb201503-dylib-hijacking.pdf
- https://malwareunicorn.org/workshops/macos_dylib_injection.html#5
- https://github.com/EmpireProject/Empire/blob/master/lib/modules/python/situational_awareness/host/osx/HijackScanner.py
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1574.004/T1574.004.md
Unlock Pro Content
Get the full detection package for T1574.004 including response playbook, investigation guide, and atomic red team tests.