Adversaries may modify the kernel to automatically execute programs on system boot. Loadable Kernel Modules (LKMs) are pieces of code that can be loaded and unloaded into the kernel upon demand. They extend the functionality of the kernel without the need to reboot the system. For example, one type of module is the device driver, which allows the kernel to access hardware connected to the system. (Citation: Linux Kernel Programming)
When used maliciously, LKMs can be a type of kernel-mode Rootkit that run with the highest operating system privilege (Ring 0). (Citation: Linux Kernel Module Programming Guide) Common features of LKM based rootkits include: hiding itself, selective hiding of files, processes and network activity, as well as log tampering, providing authenticated backdoors and enabling root access to non-privileged users. (Citation: iDefense Rootkit Overview)
Kernel extensions, also called kext, are used for macOS to load functionality onto a system similar to LKMs for Linux. They are loaded and unloaded through <code>kextload</code> and <code>kextunload</code> commands.
Adversaries can use LKMs and kexts to covertly persist on a system and elevate privileges. Examples have been found in the wild and there are some open source projects. (Citation: Volatility Phalanx2) (Citation: CrowdStrike Linux Rootkit) (Citation: GitHub Reptile) (Citation: GitHub Diamorphine)(Citation: RSAC 2015 San Francisco Patrick Wardle) (Citation: Synack Secure Kernel Extension Broken)(Citation: Securelist Ventir) (Citation: Trend Micro Skidmap)
View in MITRE ATT&CK®| Capability ID | Capability Description | Mapping Type | ATT&CK ID | ATT&CK Name | Notes |
|---|---|---|---|---|---|
| linux_auditd_alerts_and_log_analytics_agent_integration | Linux auditd alerts and Log Analytics agent integration | technique_scores | T1547.006 | Kernel Modules and Extensions |
Comments
This control may alert on a suspicious shared object file being loaded as a kernel module. No documentation is provided on the logic but kernel module loading is a relatively rare event and can only be done with a small set of commands.
References
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| file_integrity_monitoring | File Integrity Monitoring | technique_scores | T1547.006 | Kernel Modules and Extensions |
Comments
This control may detect changes to the Windows registry or files that enable Boot or Logon Autostart Execution. This control at worst scans for changes on an hourly basis.
References
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