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Description

The following analytic detects the creation of potentially malicious unsigned DLLs in the c:\windows\system32 or c:\windows\syswow64 folders. It leverages Sysmon EventCode 7 logs to identify unsigned DLLs with unavailable signatures loaded in these critical directories. This activity is significant as it may indicate a DLL hijacking attempt, a technique used by attackers to gain unauthorized access and execute malicious code. If confirmed malicious, this could lead to privilege escalation, allowing the attacker to gain elevated privileges and further compromise the target system.

  • Type: Anomaly

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

  • Last Updated: 2024-05-31
  • Author: Teoderick Contreras, Splunk
  • ID: 5a83ce44-8e0f-4786-a775-8249a525c879

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1574.002 DLL Side-Loading Persistence, Privilege Escalation, Defense Evasion
Kill Chain Phase
  • Installation
  • Exploitation
NIST
  • DE.AE
CIS20
  • CIS 10
CVE 


1
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`sysmon` EventCode=7 Signed=false OriginalFileName = "-" SignatureStatus="unavailable" ImageLoaded IN ("*:\\windows\\system32\\*", "*:\\windows\\syswow64\\*") 
| stats count min(_time) as firstTime max(_time) as lastTime by Image ImageLoaded Signed SignatureStatus OriginalFileName process_name dest EventCode ProcessId Hashes IMPHASH 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `windows_unsigned_dll_side_loading_filter`

Macros

The SPL above uses the following Macros:

:information_source: windows_unsigned_dll_side-loading_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
  • SignatureStatus
  • OriginalFileName
  • process_name
  • dest
  • EventCode
  • ProcessId
  • Hashes
  • IMPHASH

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

It is possible some Administrative utilities will load dismcore.dll outside of normal system paths, filter as needed.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
49.0 70 70 An unsigned dll module was loaded on $dest$

: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