Detection: Windows Unsigned DLL Side-Loading

Updated Date: 2024-05-31 ID: 5a83ce44-8e0f-4786-a775-8249a525c879 Author: Teoderick Contreras, Splunk Type: Anomaly Product: Splunk Enterprise Security

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.

Search

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

Data Source

Name	Platform	Sourcetype	Source	Supported App
Sysmon EventID 7	Windows	`'xmlwineventlog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`	N/A

Macros Used

Name	Value
security_content_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
windows_unsigned_dll_side_loading_filter	`search *`

windows_unsigned_dll_side_loading_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1574.002	DLL Side-Loading	Defense Evasion

KillChainPhase.EXPLOITAITON

KillChainPhase.INSTALLATION

NistCategory.DE_AE

Cis18Value.CIS_10

APT19

APT3

APT32

APT41

BRONZE BUTLER

BlackTech

Chimera

Cinnamon Tempest

Earth Lusca

FIN13

GALLIUM

Higaisa

Lazarus Group

LuminousMoth

MuddyWater

Mustang Panda

Naikon

Patchwork

SideCopy

Sidewinder

Threat Group-3390

Tropic Trooper

menuPass

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting	Value
Disabled	true
Cron Schedule	`0 * * * *`
Earliest Time	`-70m@m`
Latest Time	`-10m@m`
Schedule Window	`auto`
Creates Risk Event	True

This configuration file applies to all detections of type anomaly. These detections will use Risk Based Alerting.

Implementation

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

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
An unsigned dll module was loaded on $dest$	49	70	70

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

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-Sysmon/Operational`	`xmlwineventlog`
Integration	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-Sysmon/Operational`	`xmlwineventlog`

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: GitHub | Version: 2