Detection: Malicious PowerShell Process With Obfuscation Techniques

Updated Date: 2024-05-18 ID: cde75cf6-3c7a-4dd6-af01-27cdb4511fd4 Author: David Dorsey, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects PowerShell processes launched with command-line arguments indicative of obfuscation techniques. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on process names, parent processes, and complete command-line executions. This activity is significant because obfuscated PowerShell commands are often used by attackers to evade detection and execute malicious scripts. If confirmed malicious, this activity could lead to unauthorized code execution, privilege escalation, or persistent access within the environment, posing a significant security risk.

Search

1
2| tstats `security_content_summariesonly` count values(Processes.process) as process values(Processes.parent_process) as parent_process min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where `process_powershell` by Processes.user Processes.process_name Processes.original_file_name Processes.parent_process_name Processes.dest Processes.process 
3| `drop_dm_object_name(Processes)` 
4| `security_content_ctime(firstTime)`
5| `security_content_ctime(lastTime)`
6| eval num_obfuscation = (mvcount(split(process,"`"))-1) + (mvcount(split(process, "^"))-1) + (mvcount(split(process, "'"))-1) 
7| `malicious_powershell_process_with_obfuscation_techniques_filter` 
8| search num_obfuscation > 10

Data Source

Name	Platform	Sourcetype	Source	Supported App
Sysmon EventID 1	Windows	`'xmlwineventlog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`	N/A

Macros Used

Name	Value
process_powershell	`(Processes.process_name=pwsh.exe OR Processes.process_name=sqlps.exe OR Processes.process_name=sqltoolsps.exe OR Processes.process_name=powershell.exe OR Processes.process_name=powershell_ise.exe OR Processes.original_file_name=pwsh.dll OR Processes.original_file_name=PowerShell.EXE OR Processes.original_file_name=powershell_ise.EXE)`
malicious_powershell_process_with_obfuscation_techniques_filter	`search *`

malicious_powershell_process_with_obfuscation_techniques_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
T1059	Command and Scripting Interpreter	Execution
T1059.001	PowerShell	Execution

KillChainPhase.INSTALLATION

NistCategory.DE_CM

Cis18Value.CIS_10

APT19

APT32

APT37

APT39

Dragonfly

FIN5

FIN6

FIN7

Fox Kitten

Ke3chang

OilRig

Stealth Falcon

Whitefly

Windigo

APT19

APT28

APT29

APT3

APT32

APT33

APT38

APT39

APT41

APT5

Aquatic Panda

BRONZE BUTLER

Blue Mockingbird

Chimera

Cinnamon Tempest

Cobalt Group

Confucius

CopyKittens

DarkHydrus

DarkVishnya

Deep Panda

Dragonfly

Earth Lusca

Ember Bear

FIN10

FIN13

FIN6

FIN7

FIN8

Fox Kitten

GALLIUM

GOLD SOUTHFIELD

Gallmaker

Gamaredon Group

Gorgon Group

HAFNIUM

HEXANE

Inception

Indrik Spider

Kimsuky

Lazarus Group

LazyScripter

Leviathan

Magic Hound

Molerats

MoustachedBouncer

MuddyWater

Mustang Panda

Nomadic Octopus

OilRig

Patchwork

Poseidon Group

Sandworm Team

Sidewinder

Silence

Stealth Falcon

TA2541

TA459

TA505

TeamTNT

Threat Group-3390

Thrip

ToddyCat

Tonto Team

Turla

Volt Typhoon

WIRTE

Wizard Spider

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 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

The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the Processes node of the Endpoint data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.

Known False Positives

These characters might be legitimately on the command-line, but it is not common.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
Powershell.exe running with potential obfuscated arguments on $dest$	42	70	60

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

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: 6