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https://github.com/splunk/security_content
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Michael Haag
79 lines
4.1 KiB
YAML
79 lines
4.1 KiB
YAML
name: Malicious PowerShell Process - Encoded Command
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id: c4db14d9-7909-48b4-a054-aa14d89dbb19
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version: 16
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date: '2025-07-29'
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author: David Dorsey, Michael Haag, Splunk, SirDuckly, GitHub Community
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status: production
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type: Hunting
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description: The following analytic detects the use of the EncodedCommand parameter
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in PowerShell processes. It leverages Endpoint Detection and Response (EDR) data
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to identify variations of the EncodedCommand parameter, including shortened forms
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and different command switch types. This activity is significant because adversaries
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often use encoded commands to obfuscate malicious scripts, making detection harder.
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If confirmed malicious, this behavior could allow attackers to execute hidden code,
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potentially leading to unauthorized access, privilege escalation, or persistent
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threats within the environment. Review parallel events to determine legitimacy and
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tune based on known administrative scripts.
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data_source:
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- Sysmon EventID 1
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- Windows Event Log Security 4688
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- CrowdStrike ProcessRollup2
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search: "| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time)\
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\ as lastTime from datamodel=Endpoint.Processes where `process_powershell` by Processes.action\
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\ Processes.dest Processes.original_file_name Processes.parent_process Processes.parent_process_exec\
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\ Processes.parent_process_guid Processes.parent_process_id Processes.parent_process_name\
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\ Processes.parent_process_path Processes.process Processes.process_exec Processes.process_guid\
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\ Processes.process_hash Processes.process_id Processes.process_integrity_level\
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\ Processes.process_name Processes.process_path Processes.user Processes.user_id\
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\ Processes.vendor_product | `drop_dm_object_name(Processes)` | `security_content_ctime(firstTime)`\
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\ | `security_content_ctime(lastTime)` | where match(process,\"(?i)[\\-|\\/|\u2013\
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|\u2014|\u2015][Ee^]{1,2}[NnCcOoDdEeMmAa^]+\\s+[\\\"]?[A-Za-z0-9+/=]{5,}[\\\"]?\"\
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) | `malicious_powershell_process___encoded_command_filter`"
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how_to_implement: The detection is based on data that originates from Endpoint Detection
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and Response (EDR) agents. These agents are designed to provide security-related
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telemetry from the endpoints where the agent is installed. To implement this search,
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you must ingest logs that contain the process GUID, process name, and parent process.
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Additionally, you must ingest complete command-line executions. These logs must
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be processed using the appropriate Splunk Technology Add-ons that are specific to
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the EDR product. The logs must also be mapped to the `Processes` node of the `Endpoint`
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data model. Use the Splunk Common Information Model (CIM) to normalize the field
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names and speed up the data modeling process.
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known_false_positives: System administrators may use this option, but it's not common.
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references:
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- https://regexr.com/662ov
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- https://github.com/redcanaryco/AtomicTestHarnesses/blob/master/Windows/TestHarnesses/T1059.001_PowerShell/OutPowerShellCommandLineParameter.ps1
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- https://ss64.com/ps/powershell.html
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- https://twitter.com/M_haggis/status/1440758396534214658?s=20
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- https://www.microsoft.com/security/blog/2022/01/15/destructive-malware-targeting-ukrainian-organizations/
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- https://www.microsoft.com/en-us/security/blog/2023/05/24/volt-typhoon-targets-us-critical-infrastructure-with-living-off-the-land-techniques/
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tags:
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analytic_story:
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- CISA AA22-320A
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- Hermetic Wiper
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- Sandworm Tools
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- Qakbot
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- Volt Typhoon
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- NOBELIUM Group
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- Data Destruction
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- Lumma Stealer
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- Malicious PowerShell
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- DarkCrystal RAT
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- WhisperGate
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- Crypto Stealer
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- Microsoft SharePoint Vulnerabilities
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- Scattered Spider
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asset_type: Endpoint
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mitre_attack_id:
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- T1027
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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/T1027/atomic_red_team/windows-sysmon.log
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source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
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sourcetype: XmlWinEventLog
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