mirror of
https://github.com/splunk/security_content
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divious1
122 lines
4.6 KiB
YAML
122 lines
4.6 KiB
YAML
asset_type: Endpoint
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confidence: medium
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creation_date: '2018-03-19'
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data_metadata:
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data_models:
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- Endpoint
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data_source:
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- Endpoint Intel
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providing_technologies:
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- Carbon Black Response
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- CrowdStrike Falcon
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- Sysmon
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- Tanium
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- Ziften
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description: This search looks for PowerShell processes started with parameters used
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to bypass the local execution policy for scripts. These parameters are often observed
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in attacks leveraging PowerShell scripts as they override the default PowerShell
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execution policy.
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detect:
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splunk:
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correlation_rule:
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notable:
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drilldown_name: View powershell process information on $dest$
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drilldown_search: '| from datamodel:Endpoint.Processes | search dest="$dest$" process_id=$process_id$'
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nes_fields: dest, user, process_name
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rule_description: The system $dest$ executed a PowerShell process with parameters
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to bypass the local execution policy.
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rule_title: PowerShell process with -executionpolicy bypass detected on $dest$
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risk:
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risk_object: dest
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risk_object_type:
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- system
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risk_score: 50
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schedule:
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cron_schedule: 50 * * * *
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earliest_time: -70m@m
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latest_time: -10m@m
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search: '| tstats `security_content_summariesonly` values(Processes.process_id) as process_id,
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values(Processes.parent_process_id) as parent_process_id values(Processes.process) as process
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min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes
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where Processes.process_name=powershell.exe AND (Processes.process="* -ex*" OR Processes.process="* bypass *") by
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Processes.process_id, Processes.user, Processes.dest
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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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suppress:
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suppress_fields: dest, process_name
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suppress_period: 14400s
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eli5: This search looks for PowerShell processes that were launched using a parameter
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designed to bypass the local PowerShell execution policy. By default, the policy
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is set to "Restricted," which disables the execution of PowerShell scripts. In environments
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that make heavy use of PowerShell, the policy can be set to allow only scripts signed
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by a trusted publisher. Malicious PowerShell use almost always includes the parameter
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`-ExecutionPolicy bypass`. PowerShell is very liberal when it comes to interpreting
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command-line parameters passed to it. For example, the parameter we look for, `-ExecutionPolicy`,
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can be abbreviated to `-Execution`, `-Exec`, or even `-ex`. As such, we look for
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`* -ex*`, which should catch all variations of this parameter, followed by the keyword
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`bypass`. This search will return the host, the user the process ran under, the
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process and its command-line arguments, the number of times it has seen this process,
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and the first and last times it saw this process.
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entities:
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- dest
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- process_id
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- process
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- parent_process_id
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how_to_implement: You must be ingesting data that records process activity from your
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hosts to populate the Endpoint data model in the Processes node. You must also be
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ingesting logs with both the process name and command line from your endpoints.
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The command-line arguments are mapped to the "process" field in the Endpoint data
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model.
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id: 9be56c82-b1cc-4318-87eb-d138afaaca39
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investigations:
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- id: d8362a34-b78a-4364-9733-59b505f5b8d5
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name: Get Process Registry Activity
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type: splunk
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- id: 6a9ad4d9-6ef2-4b85-953f-a37ab256acd5
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name: Get Process File Activity
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type: splunk
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- id: bc91a8cf-35e7-4bb2-8140-e756cc06fd76
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name: Get Authentication Logs For Endpoint
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type: splunk
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- id: fecf2918-670d-4f1c-872b-3d7317a41bf9
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name: Get Parent Process Info
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type: splunk
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- id: f3fb4d1b-5f33-4b01-b541-c7af9534c242
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name: Get Notable Info
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type: splunk
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known_false_positives: There may be legitimate reasons to bypass the PowerShell execution
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policy. The PowerShell script being run with this parameter should be validated
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to ensure that it is legitimate.
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maintainers:
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- company: Splunk
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email: rvaldez@splunk.com
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name: Rico Valdez
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mappings:
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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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kill_chain_phases:
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- Command and Control
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- Actions on Objectives
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mitre_attack:
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- Execution
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- PowerShell
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- Scripting
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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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modification_date: '2018-12-03'
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name: Malicious PowerShell Process - Execution Policy Bypass
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original_authors:
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- company: Splunk
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email: rvaldez@splunk.com
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name: Rico Valdez
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references: []
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security_domain: endpoint
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spec_version: 2
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type: splunk
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version: '3.0'
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