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Description

The following analytic detects the loading of an unsigned DLL by the MMC.exe application, which is indicative of a potential UAC bypass or privilege escalation attempt. It leverages Sysmon EventCode 7 to identify instances where MMC.exe loads a non-Microsoft, unsigned DLL. This activity is significant because attackers often use this technique to modify CLSID registry entries, causing MMC.exe to load malicious DLLs, thereby bypassing User Account Control (UAC) and gaining elevated privileges. If confirmed malicious, this could allow an attacker to execute arbitrary code with higher privileges, leading to further system compromise and persistence.

  • Type: TTP

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2024-05-27
  • Author: Teoderick Contreras, Splunk
  • ID: 7f04349c-e30d-11eb-bc7f-acde48001122

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1548.002 Bypass User Account Control Privilege Escalation, Defense Evasion
T1548 Abuse Elevation Control Mechanism Privilege Escalation, Defense Evasion
T1218.014 MMC Defense Evasion
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


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`sysmon` EventCode=7  ImageLoaded = "*.dll" Image = "*\\mmc.exe" Signed=false Company != "Microsoft Corporation" 
| stats count min(_time) as firstTime max(_time) as lastTime by Image ImageLoaded Signed ProcessId OriginalFileName dest EventCode Company 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `uac_bypass_mmc_load_unsigned_dll_filter`

Macros

The SPL above uses the following Macros:

:information_source: uac_bypass_mmc_load_unsigned_dll_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • Image
  • ImageLoaded
  • Signed
  • ProcessId
  • OriginalFileName
  • dest
  • EventCode
  • Company

How To Implement

To successfully implement this search, you need to be ingesting logs with the process name and imageloaded executions from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA.

Known False Positives

unknown. all of the dll loaded by mmc.exe is microsoft signed dll.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
63.0 70 90 Suspicious unsigned $ImageLoaded$ loaded by $Image$ on endpoint $dest$ with EventCode $EventCode$

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

source | version: 2