Execution via local SxS Shared Module

Identifies the creation, change, or deletion of a DLL module within a Windows SxS local folder. Adversaries may abuse shared modules to execute malicious payloads by instructing the Windows module loader to load DLLs from arbitrary local paths.

Rule type: eql

Rule indices:

winlogbeat-*
logs-endpoint.events.*
logs-windows.*

Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

https://docs.microsoft.com/en-us/windows/win32/dlls/dynamic-link-library-redirection

Tags:

Elastic
Host
Windows
Threat Detection
Execution

Version: 8

Rule authors:

Elastic

Rule license: Elastic License v2

Investigation guide

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## Triage and analysis

The SxS DotLocal folder is a legitimate feature that can be abused to hijack standard modules loading order by forcing an executable on the same application.exe.local folder to load a malicious DLL module from the same directory.

## Setup

If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2, events will not define `event.ingested` and default fallback for EQL rules was not added until 8.2, so you will need to add a custom pipeline to populate `event.ingested` to @timestamp for this rule to work.

Rule query

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file where file.extension : "dll" and file.path : "C:\\*\\*.exe.local\\*.dll"

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Execution
- ID: TA0002
- Reference URL: https://attack.mitre.org/tactics/TA0002/
Technique:
- Name: Shared Modules
- ID: T1129
- Reference URL: https://attack.mitre.org/techniques/T1129/

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