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* Add YAML formatting and validation infrastructure - Add yamlfmt configuration (.yamlfmt) with 4-space indent, LF line endings - Add yamllint configuration (.yamllint) for syntax validation (detections/ only) - Add pre-commit hook for automatic YAML formatting - Add CI validation script with unified error output - Add GitHub Actions workflow for PR validation - Add documentation for setup and usage - Support custom yamlfmt binary path via --yamlfmt-path flag * comment yaml check from pre-commit * apply yamlfmt * Update yaml-validation.yml * Update yaml-validation.yml * application folder search formatting * cloud folder search formatting * web folder search formatting * network folder search formatting * endpoint folder search formatting * resolve first conflict * apply formatting * remove additional pipe * Update README.md * update versions * restore and update formatting (#3920) --------- Co-authored-by: Bhavin Patel <bhavin.j.patel91@gmail.com>
53 lines
3.4 KiB
YAML
53 lines
3.4 KiB
YAML
name: Windows DiskCryptor Usage
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id: d56fe0c8-4650-11ec-a8fa-acde48001122
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version: 8
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date: '2026-02-25'
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author: Michael Haag, Splunk
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status: production
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type: Hunting
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description: The following analytic detects the execution of DiskCryptor, identified by the process names "dcrypt.exe" or "dcinst.exe". This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on process names and original file names. DiskCryptor is significant because adversaries use it to manually encrypt disks during an operation, potentially leading to data inaccessibility. If confirmed malicious, this activity could result in complete disk encryption, causing data loss and operational disruption. Immediate investigation is required to mitigate potential ransomware attacks.
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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: |-
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| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes
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WHERE (
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Processes.process_name="dcrypt.exe"
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OR
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Processes.original_file_name=dcinst.exe
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)
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BY Processes.action Processes.dest Processes.original_file_name
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Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid
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Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path
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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
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Processes.user_id Processes.vendor_product
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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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| `windows_diskcryptor_usage_filter`
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how_to_implement: The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the `Processes` node of the `Endpoint` data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.
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known_false_positives: It is possible false positives may be present based on the internal name dcinst.exe, filter as needed. It may be worthy to alert on the service name.
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references:
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- https://thedfirreport.com/2021/11/15/exchange-exploit-leads-to-domain-wide-ransomware/
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- https://github.com/DavidXanatos/DiskCryptor
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tags:
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analytic_story:
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- Ransomware
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asset_type: Endpoint
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mitre_attack_id:
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- T1486
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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/T1486/dcrypt/windows-sysmon.log
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source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
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sourcetype: XmlWinEventLog
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