Detection: PowerShell Script Block With URL Chain

Updated Date: 2024-05-30 ID: 4a3f2a7d-6402-4e64-a76a-869588ec3b57 Author: Steven Dick Type: TTP Product: Splunk Enterprise Security

Description

The following analytic identifies suspicious PowerShell script execution via EventCode 4104 that contains multiple URLs within a function or array. It leverages PowerShell operational logs to detect script blocks with embedded URLs, often indicative of obfuscated scripts or those attempting to download secondary payloads. This activity is significant as it may signal an attempt to execute malicious code or download additional malware. If confirmed malicious, this could lead to code execution, further system compromise, or data exfiltration. Review parallel processes and the full script block for additional context and related artifacts.

 1`powershell` EventCode=4104 ScriptBlockText IN ("*http:*","*https:*") 
 2| regex ScriptBlockText="(\"?(https?:\/\/(?:www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b(?:[-a-zA-Z0-9()@:%_\+.~#?&\/=]*))\"?(?:,
 3|\))?){2,}" 
 4| rex max_match=20 field=ScriptBlockText "(?<url>https?:\/\/(?:www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b(?:[-a-zA-Z0-9()@:%_\+.~#?&\/=]*))" 
 5| eval Path = case(isnotnull(Path),Path,true(),"unknown") 
 6| stats count min(_time) as firstTime max(_time) as lastTime list(ScriptBlockText) as command values(Path) as file_name values(UserID) as user values(url) as url dc(url) as url_count by ActivityID, Computer, EventCode 
 7| rename Computer as dest, EventCode as signature_id 
 8| `security_content_ctime(firstTime)` 
 9| `security_content_ctime(lastTime)` 
10| `powershell_script_block_with_url_chain_filter`

Data Source

Name Platform Sourcetype Source Supported App
Powershell Script Block Logging 4104 Windows icon Windows 'xmlwineventlog' 'XmlWinEventLog:Microsoft-Windows-PowerShell/Operational' N/A

Macros Used

Name Value
powershell (source=WinEventLog:Microsoft-Windows-PowerShell/Operational OR source="XmlWinEventLog:Microsoft-Windows-PowerShell/Operational")
powershell_script_block_with_url_chain_filter search *
powershell_script_block_with_url_chain_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
T1059.001 PowerShell Execution
T1105 Ingress Tool Transfer Command And Control
KillChainPhase.COMMAND_AND_CONTROL
KillChainPhase.INSTALLATION
NistCategory.DE_CM
Cis18Value.CIS_10
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
APT-C-36
APT18
APT28
APT29
APT3
APT32
APT33
APT37
APT38
APT39
APT41
Ajax Security Team
Andariel
Aquatic Panda
BITTER
BRONZE BUTLER
BackdoorDiplomacy
Chimera
Cinnamon Tempest
Cobalt Group
Confucius
Darkhotel
Dragonfly
Elderwood
Ember Bear
Evilnum
FIN13
FIN7
FIN8
Fox Kitten
GALLIUM
Gamaredon Group
Gorgon Group
HAFNIUM
HEXANE
IndigoZebra
Indrik Spider
Ke3chang
Kimsuky
Lazarus Group
LazyScripter
Leviathan
LuminousMoth
Magic Hound
Metador
Molerats
Moses Staff
MuddyWater
Mustang Panda
Mustard Tempest
Nomadic Octopus
OilRig
PLATINUM
Patchwork
Rancor
Rocke
Sandworm Team
SideCopy
Sidewinder
Silence
TA2541
TA505
TA551
TeamTNT
Threat Group-3390
Tonto Team
Tropic Trooper
Turla
Volatile Cedar
WIRTE
Whitefly
Windshift
Winnti Group
Wizard Spider
ZIRCONIUM
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 following analytic requires PowerShell operational logs to be imported. Modify the powershell macro as needed to match the sourcetype or add index. This analytic is specific to 4104, or PowerShell Script Block Logging.

Known False Positives

Unknown, possible custom scripting.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
A suspicious powershell script used by $user$ on host $dest$ contains $url_count$ URLs in an array, this is commonly used for malware. 80 100 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-PowerShell/Operational XmlWinEventLog
Integration ✅ Passing Dataset XmlWinEventLog:Microsoft-Windows-PowerShell/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