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https://github.com/splunk/security_content
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tccontre
72 lines
3.0 KiB
YAML
72 lines
3.0 KiB
YAML
name: Powershell Processing Stream Of Data
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id: 0d718b52-c9f1-11eb-bc61-acde48001122
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version: 2
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date: '2022-02-25'
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author: Teoderick Contreras, Splunk
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type: TTP
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datamodel: []
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description: The following analytic identifies suspicious PowerShell script execution
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via EventCode 4104 that is processing compressed stream data. This is typically
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found in obfuscated PowerShell or PowerShell executing embedded .NET or binary files
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that are stream flattened and will be deflated durnig execution. During triage,
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review parallel processes within the same timeframe. Review the full script block
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to identify other related artifacts.
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search: '`powershell` EventCode=4104 ScriptBlockText = "*IO.Compression.*" OR ScriptBlockText = "*IO.StreamReader*"
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OR ScriptBlockText = "*]::Decompress*" | stats count min(_time) as firstTime max(_time)
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as lastTime by EventCode ScriptBlockText Computer UserID | `security_content_ctime(firstTime)`
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| `security_content_ctime(lastTime)` | `powershell_processing_stream_of_data_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: powershell may used this function to process compressed data.
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references:
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- https://medium.com/@ahmedjouini99/deobfuscating-emotets-powershell-payload-e39fb116f7b9
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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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- https://blog.palantir.com/tampering-with-windows-event-tracing-background-offense-and-defense-4be7ac62ac63
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- https://static1.squarespace.com/static/552092d5e4b0661088167e5c/t/59c1814829f18782e24f1fe2/1505853768977/Windows+PowerShell+Logging+Cheat+Sheet+ver+Sept+2017+v2.1.pdf
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- https://www.crowdstrike.com/blog/investigating-powershell-command-and-script-logging/
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- https://www.splunk.com/en_us/blog/security/hunting-for-malicious-powershell-using-script-block-logging.html
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tags:
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analytic_story:
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- Hermetic Wiper
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- Malicious PowerShell
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- AsyncRAT
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confidence: 80
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context:
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- Source:Endpoint
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- Stage:Defense Evasion
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dataset:
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- https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1059.001/powershell_script_block_logging/streamreader.log
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impact: 50
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kill_chain_phases:
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- Exploitation
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message: A suspicious powershell script contains stream command in $ScriptBlockText$ commonly
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for processing compressed or to decompressed binary file with EventCode $EventCode$
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in host $Computer$
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mitre_attack_id:
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- T1059
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- T1059.001
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observable:
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- name: Computer
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type: Hostname
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role:
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- Victim
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- name: UserID
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type: User
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role:
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- Victim
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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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required_fields:
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- _time
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- EventCode
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- ScriptBlockText
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- Computer
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- UserID
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- Score
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risk_score: 40
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security_domain: endpoint
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asset_type: Endpoint
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