Detection: Windows Powershell Cryptography Namespace

Description

The following analytic detects suspicious PowerShell script execution involving the cryptography namespace via EventCode 4104. It leverages PowerShell Script Block Logging to identify scripts using cryptographic functions, excluding common hashes like SHA and MD5. This activity is significant as it is often associated with malware that decrypts or decodes additional malicious payloads. If confirmed malicious, this could allow an attacker to execute further code, escalate privileges, or establish persistence within the environment. Analysts should investigate the parent process, decrypted data, network connections, and the user executing the script.

1`powershell` EventCode=4104 ScriptBlockText = "*System.Security.Cryptography*" AND NOT(ScriptBlockText IN ("*SHA*", "*MD5*", "*DeriveBytes*")) 
2| stats count min(_time) as firstTime max(_time) as lastTime by EventCode ScriptBlockText Computer UserID 
3| rename Computer as dest 
4| rename UserID as user 
5| `security_content_ctime(firstTime)` 
6| `security_content_ctime(lastTime)` 
7| `windows_powershell_cryptography_namespace_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")
windows_powershell_cryptography_namespace_filter search *
windows_powershell_cryptography_namespace_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
T1059 Command and Scripting Interpreter Execution
KillChainPhase.INSTALLATION
NistCategory.DE_AE
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
APT19
APT32
APT37
APT39
Dragonfly
FIN5
FIN6
FIN7
Fox Kitten
Ke3chang
OilRig
Stealth Falcon
Whitefly
Windigo

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 analytic, you will need to enable PowerShell Script Block Logging on some or all endpoints. Additional setup here https://docs.splunk.com/Documentation/UBA/5.0.4.1/GetDataIn/AddPowerShell#Configure_module_logging_for_PowerShell.

Known False Positives

False positives should be limited. Filter as needed.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message Risk Score Impact Confidence
A suspicious powershell script contains cryptography command detected on host $dest$ 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

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: 3