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mhaag-spl
78 lines
3.3 KiB
YAML
78 lines
3.3 KiB
YAML
name: Malicious PowerShell Process - Encoded Command
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id: c4db14d9-7909-48b4-a054-aa14d89dbb19
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version: 6
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date: '2021-10-05'
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author: David Dorsey, Michael Haag, Splunk
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type: Hunting
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datamodel:
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- Endpoint
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description: 'The following analytic identifies the use of the EncodedCommand PowerShell parameter. This is typically used by Administrators to run complex scripts, but commonly used by adversaries to hide their code. \
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The analytic identifies all variations of EncodedCommand, as PowerShell allows the ability to shorten the parameter. For example enc, enco, encod and so forth. In addition, through our research it was identified that PowerShell will interpret different command switch types beyond the hyphen. We have added endash, emdash, horizontal bar, and forward slash. \
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During triage, review parallel events to determine legitimacy. Tune as needed based on admin scripts in use. \
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Alternatively, may use regex per matching here https://regexr.com/662ov.'
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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.user
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Processes.process_name Processes.process Processes.parent_process_name Processes.original_file_name Processes.dest Processes.process_id
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| `drop_dm_object_name(Processes)`
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| `security_content_ctime(firstTime)`
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| `security_content_ctime(lastTime)`
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| where match(process,"(?i)[\-|\/|–|—|―]e(nc*o*d*e*d*c*o*m*m*a*n*d*)*\s+[^-]")
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| `malicious_powershell_process___encoded_command_filter`'
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how_to_implement: To successfully implement this search you need to be ingesting information on process that include the name of the process responsible for the changes from your endpoints into the `Endpoint` datamodel in the `Processes` node. In addition, confirm the latest CIM App 4.20 or higher is installed and the latest TA for the endpoint product.
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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/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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tags:
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analytic_story:
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- Malicious PowerShell
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- NOBELIUM Group
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asset_type: Endpoint
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automated_detection_testing: passed
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cis20:
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- CIS 3
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- CIS 7
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- CIS 8
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confidence: 50
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context:
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- Source:Endpoint
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- Stage:Initial Access
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- Stage:Execution
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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/T1027/atomic_red_team/windows-sysmon.log
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impact: 70
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kill_chain_phases:
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- Command and Control
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- Actions on Objectives
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message: Powershell.exe running potentially malicious encodede commands on $dest$
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mitre_attack_id:
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- T1027
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nist:
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- PR.PT
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- DE.CM
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- PR.IP
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observable:
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- name: dest
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type: Endpoint
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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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- Processes.process_name
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- Processes.process
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- Processes.user
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- Processes.parent_process_name
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- Processes.dest
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- Processes.process_id
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risk_score: 35
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security_domain: endpoint |