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https://github.com/splunk/security_content
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Eric
72 lines
3.4 KiB
YAML
72 lines
3.4 KiB
YAML
name: Windows Powershell Cryptography Namespace
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id: f8b482f4-6d62-49fa-a905-dfa15698317b
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version: 8
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date: '2025-05-02'
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author: Teoderick Contreras, Splunk
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status: production
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type: Anomaly
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description: The following analytic detects suspicious PowerShell script execution
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involving the cryptography namespace via EventCode 4104. It leverages PowerShell
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Script Block Logging to identify scripts using cryptographic functions, excluding
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common hashes like SHA and MD5. This activity is significant as it is often associated
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with malware that decrypts or decodes additional malicious payloads. If confirmed
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malicious, this could allow an attacker to execute further code, escalate privileges,
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or establish persistence within the environment. Analysts should investigate the
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parent process, decrypted data, network connections, and the user executing the
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script.
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data_source:
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- Powershell Script Block Logging 4104
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search: '`powershell` EventCode=4104 ScriptBlockText = "*System.Security.Cryptography*"
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AND NOT(ScriptBlockText IN ("*SHA*", "*MD5*", "*DeriveBytes*")) | fillnull | stats
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count min(_time) as firstTime max(_time) as lastTime by dest signature signature_id
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user_id vendor_product EventID Guid Opcode Name Path ProcessID ScriptBlockId ScriptBlockText
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| `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `windows_powershell_cryptography_namespace_filter`'
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how_to_implement: To successfully implement this analytic, you will need to enable
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PowerShell Script Block Logging on some or all endpoints. Additional setup here
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https://docs.splunk.com/Documentation/UBA/5.0.4.1/GetDataIn/AddPowerShell#Configure_module_logging_for_PowerShell.
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known_false_positives: False positives should be limited. Filter as needed.
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references:
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- https://malpedia.caad.fkie.fraunhofer.de/details/win.asyncrat
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drilldown_searches:
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- name: View the detection results for - "$dest$" and "$user_id$"
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search: '%original_detection_search% | search dest = "$dest$" user_id = "$user_id$"'
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earliest_offset: $info_min_time$
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latest_offset: $info_max_time$
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- name: View risk events for the last 7 days for - "$dest$" and "$user_id$"
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search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$",
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"$user_id$") starthoursago=168 | stats count min(_time) as firstTime max(_time)
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as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk
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Message" values(analyticstories) as "Analytic Stories" values(annotations._all)
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as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics"
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by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
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earliest_offset: $info_min_time$
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latest_offset: $info_max_time$
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rba:
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message: A suspicious powershell script contains cryptography command detected on
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host $dest$
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risk_objects:
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- field: dest
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type: system
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score: 25
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- field: user_id
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type: user
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score: 25
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threat_objects: []
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tags:
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analytic_story:
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- AsyncRAT
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asset_type: Endpoint
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mitre_attack_id:
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- T1059.001
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product:
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- Splunk Enterprise
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- Splunk Enterprise Security
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- Splunk Cloud
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security_domain: endpoint
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tests:
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- name: True Positive Test
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attack_data:
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- data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1059.001/asyncrat_crypto_pwh_namespace/windows-powershell-xml.log
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source: XmlWinEventLog:Microsoft-Windows-PowerShell/Operational
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sourcetype: XmlWinEventLog
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