Detection: Windows User Execution Malicious URL Shortcut File

Updated Date: 2024-05-16 ID: 5c7ee6ad-baf4-44fb-b2f0-0cfeddf82dbc Author: Teoderick Contreras, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects the creation of suspicious URL shortcut link files, often used by malware like CHAOS ransomware. It leverages the Endpoint.Filesystem datamodel to identify .url files created outside standard directories, such as Program Files. This activity is significant as it may indicate an attempt to execute malicious code upon system reboot. If confirmed malicious, this could allow an attacker to achieve persistence and execute harmful payloads, potentially leading to further system compromise and data loss.

Search

1
2|tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Filesystem where NOT(Filesystem.file_path IN ("*\\Program Files*")) Filesystem.file_name = *.url by Filesystem.file_create_time Filesystem.process_id  Filesystem.file_name Filesystem.user Filesystem.file_path Filesystem.process_guid Filesystem.dest 
3| `drop_dm_object_name(Filesystem)` 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `windows_user_execution_malicious_url_shortcut_file_filter`

Data Source

Name	Platform	Sourcetype	Source	Supported App
Sysmon EventID 11	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_user_execution_malicious_url_shortcut_file_filter	`search *`

windows_user_execution_malicious_url_shortcut_file_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
T1204.002	Malicious File	Execution
T1204	User Execution	Execution

KillChainPhase.INSTALLATION

NistCategory.DE_CM

Cis18Value.CIS_10

APT-C-36

APT12

APT19

APT28

APT29

APT30

APT32

APT33

APT37

APT38

APT39

Ajax Security Team

Andariel

Aoqin Dragon

BITTER

BRONZE BUTLER

BlackTech

CURIUM

Cobalt Group

Confucius

Dark Caracal

DarkHydrus

Darkhotel

Dragonfly

EXOTIC LILY

Earth Lusca

Elderwood

Ember Bear

FIN4

FIN6

FIN7

FIN8

Ferocious Kitten

Gallmaker

Gamaredon Group

Gorgon Group

HEXANE

Higaisa

Inception

IndigoZebra

Indrik Spider

Kimsuky

Lazarus Group

LazyScripter

Leviathan

Machete

Magic Hound

Malteiro

Mofang

Molerats

MuddyWater

Mustang Panda

Naikon

Nomadic Octopus

OilRig

PLATINUM

PROMETHIUM

Patchwork

RTM

Rancor

Sandworm Team

SideCopy

Sidewinder

Silence

TA2541

TA459

TA505

TA551

The White Company

Threat Group-3390

Tonto Team

Transparent Tribe

Tropic Trooper

WIRTE

Whitefly

Windshift

Wizard Spider

admin@338

menuPass

LAPSUS$

Scattered 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

To successfully implement this search you need to be ingesting information on process that include the name of the Filesystem responsible for the changes from your endpoints into the Endpoint datamodel in the Filesystem node.

Known False Positives

Administrators may allow creation of script or exe in this path.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
a process created URL shortcut file in $file_path$ of $dest$	64	80	80

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