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Eric
61 lines
3.2 KiB
YAML
61 lines
3.2 KiB
YAML
name: Windows DiskCryptor Usage
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id: d56fe0c8-4650-11ec-a8fa-acde48001122
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version: 7
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date: '2025-05-02'
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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
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by the process names "dcrypt.exe" or "dcinst.exe". This detection leverages data
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from Endpoint Detection and Response (EDR) agents, focusing on process names and
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original file names. DiskCryptor is significant because adversaries use it to manually
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encrypt disks during an operation, potentially leading to data inaccessibility.
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If confirmed malicious, this activity could result in complete disk encryption,
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causing data loss and operational disruption. Immediate investigation is required
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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: '| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time)
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as lastTime from datamodel=Endpoint.Processes where (Processes.process_name="dcrypt.exe"
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OR Processes.original_file_name=dcinst.exe) 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 Processes.process_hash
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Processes.process_id Processes.process_integrity_level Processes.process_name Processes.process_path
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Processes.user Processes.user_id Processes.vendor_product | `drop_dm_object_name(Processes)`
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| `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `windows_diskcryptor_usage_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: It is possible false positives may be present based on the
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internal name dcinst.exe, filter as needed. It may be worthy to alert on the service
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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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