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LSASS Driver

The Windows security subsystem is a set of components that manage and enforce the security policy for a computer or domain. The Local Security Authority (LSA) is the main component responsible for local security policy and user authentication. The LSA includes multiple dynamic link libraries (DLLs) associated with various other security functions, all of which run in the context of the LSA Subsystem Service (LSASS) lsass.exe process. [1]

Adversaries may target lsass.exe drivers to obtain execution and/or persistence. By either replacing or adding illegitimate drivers (e.g., DLL Side-Loading or DLL Search Order Hijacking), an adversary can achieve arbitrary code execution triggered by continuous LSA operations.

ID: T1177

Tactic: Execution, Persistence

Platform:  Windows

Permissions Required:  Administrator, SYSTEM

Data Sources:  API monitoring, DLL monitoring, File monitoring, Kernel drivers, Loaded DLLs, Process monitoring

Supports Remote:  No

Contributors:  Vincent Le Toux

Version: 1.0

Examples

NameDescription
Pasam

Pasam establishes by infecting the Security Accounts Manager (SAM) DLL to load a malicious DLL dropped to disk.[2]

Wingbird

Wingbird drops a malicious file (sspisrv.dll) alongside a copy of lsass.exe, which is used to register a service that loads sspisrv.dll as a driver. The payload of the malicious driver (located in its entry-point function) is executed when loaded by lsass.exe before the spoofed service becomes unstable and crashes.[3][4]

Mitigation

On Windows 8.1 and Server 2012 R2, enable LSA Protection by setting the Registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\RunAsPPL to dword:00000001. [5] LSA Protection ensures that LSA plug-ins and drivers are only loaded if they are digitally signed with a Microsoft signature and adhere to the Microsoft Security Development Lifecycle (SDL) process guidance.

On Windows 10 and Server 2016, enable Windows Defender Credential Guard [6] to run lsass.exe in an isolated virtualized environment without any device drivers. [7]

Ensure safe DLL search mode is enabled HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\SafeDllSearchMode to mitigate risk that lsass.exe loads a malicious code library. [8]

Detection

With LSA Protection enabled, monitor the event logs (Events 3033 and 3063) for failed attempts to load LSA plug-ins and drivers. [5]

Utilize the Sysinternals Autoruns/Autorunsc utility [9] to examine loaded drivers associated with the LSA.

Utilize the Sysinternals Process Monitor utility to monitor DLL load operations in lsass.exe. [8]

References