Windows Powershell Cryptography Namespace

name: Windows Powershell Cryptography Namespace
id: f8b482f4-6d62-49fa-a905-dfa15698317b
version: 16
creation_date: '2023-01-26'
modification_date: '2026-06-25'
author: Teoderick Contreras, Splunk
status: production
type: Anomaly
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.
data_source:
    - Powershell Script Block Logging 4104
search: |-
    `powershell` EventCode=4104 ScriptBlockText = "*System.Security.Cryptography*" AND NOT(ScriptBlockText IN ("*SHA*", "*MD5*", "*DeriveBytes*"))
      | fillnull
      | stats count min(_time) as firstTime max(_time) as lastTime
        BY dest signature signature_id
           user_id vendor_product EventID
           Guid Opcode Name
           Path ProcessID ScriptBlockId
           ScriptBlockText
      | `security_content_ctime(firstTime)`
      | `security_content_ctime(lastTime)`
      | `windows_powershell_cryptography_namespace_filter`
how_to_implement: To successfully implement this analytic, you will need to enable PowerShell Script Block Logging on some or all endpoints. Additional setup here https://help.splunk.com/en/security-offerings/splunk-user-behavior-analytics/get-data-in/5.4.1/add-other-data-to-splunk-uba/configure-powershell-logging-to-see-powershell-anomalies-in-splunk-uba.
known_false_positives: False positives should be limited. Filter as needed.
references:
    - https://malpedia.caad.fkie.fraunhofer.de/details/win.asyncrat
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 20
          message: A suspicious powershell script contains cryptography command detected on host $dest$
        - field: user_id
          type: user
          score: 20
          message: A suspicious powershell script contains cryptography command detected on host $dest$
analytic_story:
    - AsyncRAT
    - XWorm
    - VIP Keylogger
    - Phantom Stealer
asset_type: Endpoint
mitre_attack_id:
    - T1059.001
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint