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https://github.com/splunk/security_content
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Eric
81 lines
3.9 KiB
YAML
81 lines
3.9 KiB
YAML
name: Powershell Creating Thread Mutex
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id: 637557ec-ca08-11eb-bd0a-acde48001122
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version: 10
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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: TTP
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description:
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The following analytic detects the execution of PowerShell scripts using
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the `mutex` function via EventCode 4104. This detection leverages PowerShell Script
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Block Logging to identify scripts that create thread mutexes, a technique often
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used in obfuscated scripts to ensure only one instance runs on a compromised machine.
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This activity is significant as it may indicate the presence of sophisticated malware
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or persistence mechanisms. If confirmed malicious, the attacker could maintain exclusive
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control over a process, potentially leading to further exploitation or persistence
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within the environment.
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data_source:
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- Powershell Script Block Logging 4104
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search:
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'`powershell` EventCode=4104 ScriptBlockText = "*Threading.Mutex*" | fillnull
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| stats 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)` | `powershell_creating_thread_mutex_filter`'
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how_to_implement:
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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:
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powershell developer may used this function in their script
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for instance checking too.
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references:
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- https://isc.sans.edu/forums/diary/Some+Powershell+Malicious+Code/22988/
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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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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:
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'| 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 Thread Mutex on 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: 40
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- field: user_id
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type: user
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score: 40
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threat_objects: []
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tags:
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analytic_story:
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- Malicious PowerShell
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- Water Gamayun
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asset_type: Endpoint
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mitre_attack_id:
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- T1027.005
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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/powershell_script_block_logging/sbl_xml.log
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source: XmlWinEventLog:Microsoft-Windows-PowerShell/Operational
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sourcetype: XmlWinEventLog
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