Query: explain T1547.006 Kernel Modules and Extensions
Matching passage: T1547.006 Kernel Modules and Extensions. Tactics: persistence, privilege escalation. Description: 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](https://attack.mitre.org/techniques/T1014) 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 in macOS to load functionality onto a system similar to LKMs for Linux. Since the kernel is responsible for enforcing security and the kernel extensions run as apart of the kernel, kexts are not governed by macOS security policies. Kexts are loaded and unloaded through <code>kextload</code> and <code>kextunload</code> commands. Kexts need to be signed with a developer ID that is granted privileges by Apple allowing it to sign Kernel extensions. Developers without these privileges may still sign kexts but they will not load unless SIP is disabled. If SIP is enabled, the kext signature is verified before being added to the AuxKC.(Citation: System and kernel extensions in macOS) Since macOS Catalina 10.15, kernel extensions have been deprecated in favor of System Extensions. However, kexts are still allowed as "Legacy System Extensions" since there is no System Extension for Kernel Programming Interfaces.(Citation: Apple Kernel Extension Deprecation) Adversaries can use LKMs and kexts to conduct [Persistence](https
Near-miss passage: T1547.003 Time Providers. Tactics: persistence, privilege escalation. Description: Adversaries may abuse time providers to execute DLLs when the system boots. The Windows Time service (W32Time) enables time synchronization across and within domains.(Citation: Microsoft W32Time Feb 2018) W32Time time providers are responsible for retrieving time stamps from hardware/network resources and outputting these values to other network clients.(Citation: Microsoft TimeProvider) Time providers are implemented as dynamic-link libraries (DLLs) that are registered in the subkeys of `HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\W32Time\TimeProviders\`.(Citation: Microsoft TimeProvider) The time provider manager, directed by the service control manager, loads and starts time providers listed and enabled under this key at system startup and/or whenever parameters are changed.(Citation: Microsoft TimeProvider) Adversaries may abuse this architecture to establish persistence, specifically by creating a new arbitrarily named subkey pointing to a malicious DLL in the `DllName` value. Administrator privileges are required for time provider registration, though execution will run in context of the Local Service account.(Citation: Github W32Time Oct 2017)