Detection: Unsigned Image Loaded by LSASS

DEPRECATED DETECTION

This detection has been marked as deprecated by the Splunk Threat Research team. This means that it will no longer be maintained or supported. If you have any questions or concerns, please reach out to us at research@splunk.com.

Updated Date: 2024-10-17 ID: 56ef054c-76ef-45f9-af4a-a634695dcd65 Author: Patrick Bareiss, Splunk Type: TTP Product: Splunk Enterprise Security

Description

This search detects loading of unsigned images by LSASS. Deprecated because too noisy.

Search

1`sysmon` EventID=7 Image=*lsass.exe Signed=false 
2| stats count min(_time) as firstTime max(_time) as lastTime by dest, Image, ImageLoaded, Signed, SHA1 
3| `security_content_ctime(firstTime)`
4| `security_content_ctime(lastTime)` 
5| `unsigned_image_loaded_by_lsass_filter`

Data Source

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

Macros Used

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

unsigned_image_loaded_by_lsass_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
T1003.001	LSASS Memory	Credential Access

KillChainPhase.EXPLOITAITON

NistCategory.DE_CM

Cis18Value.CIS_10

APT1

APT28

APT3

APT32

APT33

APT39

APT41

APT5

Agrius

Aquatic Panda

BRONZE BUTLER

Blue Mockingbird

Cleaver

Earth Lusca

Ember Bear

FIN13

FIN6

FIN8

Fox Kitten

GALLIUM

HAFNIUM

Indrik Spider

Ke3chang

Kimsuky

Leafminer

Leviathan

Magic Hound

Moonstone Sleet

MuddyWater

OilRig

PLATINUM

Play

RedCurl

Sandworm Team

Silence

Threat Group-3390

Volt Typhoon

Whitefly

Wizard Spider

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 Notable	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Risk Event	True

This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

This search needs Sysmon Logs with a sysmon configuration, which includes EventCode 7 with lsass.exe. This search uses an input macro named sysmon. We strongly recommend that you specify your environment-specific configurations (index, source, sourcetype, etc.) for Windows Sysmon logs. Replace the macro definition with configurations for your Splunk environment. The search also uses a post-filter macro designed to filter out known false positives.

Known False Positives

Other tools could load images into LSASS for legitimate reason. But enterprise tools should always use signed DLLs.

Associated Analytic Story

Credential Dumping

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
tbd	25	50	50

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

https://2017.zeronights.org/wp-content/uploads/materials/ZN17_Kheirkhabarov_Hunting_for_Credentials_Dumping_in_Windows_Environment.pdf

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	Not Applicable	N/A	N/A	N/A
Unit	❌ Failing	N/A	`N/A`	`N/A`
Integration	❌ Failing	N/A	`N/A`	`N/A`

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: 3