splunk-security_content/detections/unusually_long_commandlines_mltk.yml

asset_type: ''
baselines:
  - id: d2a4d85b-fc6a-47a0-82f6-bc1ec2ebc459
    name: Baseline of Command Line Length - MLTK
    type: splunk
confidence: medium
creation_date: '2019-05-08'
data_metadata:
  data_models:
    - Endpoint
  data_source:
    - Endpoint Intel
  providing_technologies:
    - Carbon Black Response
    - CrowdStrike Falcon
    - Sysmon
    - Tanium
    - Ziften
description: Command lines that are extremely long may be indicative of malicious
  activity on your hosts. This search leverages the Machine Learning Toolkit (MLTK)
  to help identify command lines with lengths that are unusual for a given user.
detect:
  splunk:
    correlation_rule:
      notable:
        nes_fields: dest, process, user
        rule_description: An unusually long command line $cmdline$ was found on $dest$
        rule_title: Unusually Long Command Line on $dest$
      risk:
        risk_object: dest
        risk_object_type:
          - system
        risk_score: 50
      schedule:
        cron_schedule: 0 * * * *
        earliest_time: -70m@m
        latest_time: -10m@m
      search: '| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes by Processes.user Processes.dest Processes.process_name Processes.process | `drop_dm_object_name(Processes)` | `security_content_ctime(firstTime)`| `security_content_ctime(lastTime)`| eval processlen=len(process) | search user!=unknown | apply cmdline_pdfmodel threshold=0.01 | rename "IsOutlier(processlen)" as isOutlier | search isOutlier > 0 | table firstTime lastTime user dest process_name process processlen count'
      suppress:
        suppress_fields: dest,user,process_name
        suppress_period: 28800s
eli5: This search leverages the Machine Learning Toolkit (MLTK) to identify outliers
  in the length of the command lines observed to be used by a specific user. The companion
  search, "Baseline of Command Line Length - MLTK," creates a machine-learning (ML)
  model built over the historical data used by this search. The determination of what
  is considered an outlier may be adjusted via the threshold parameter in the search.
  More information on the algorithm used can be found at `https://docs.splunk.com/Documentation/MLApp/4.2.0/User/Algorithms#DensityFunction`.
entities:
  - dest
  - process_name
  - user
how_to_implement: You must be ingesting endpoint data that monitors command lines
  and populates the Endpoint data model in the Processes node. The command-line arguments
  are mapped to the "process" field in the Endpoint data model. In addition, MLTK
  version >= 4.2 must be installed on your search heads, along with any required dependencies.
  Finally, the support search "Baseline of Command Line Length - MLTK" must be executed
  before this detection search, as it builds an ML model over the historical data
  used by this search. It is important that this search is run in the same app context
  as the associated support search, so that the model created by the support search
  is available for use. You should periodically re-run the support search to rebuild
  the model with the latest data available in your environment.
id: 57edaefa-a73b-45e5-bbae-f39c1473f941
investigations:
  - id: bc91a8cf-35e7-4bb2-8140-e756cc06fd76
    name: Get Authentication Logs For Endpoint
    type: splunk
  - id: fecf2918-670d-4f1c-872b-3d7317a41bf9
    name: Get Parent Process Info
    type: splunk
  - id: fdcfb369-1725-4c24-824a-22972d7f0d55
    name: Get Risk Modifiers For User
    type: splunk
  - id: bc91a8cf-35e7-4bb2-8140-e756cc06fd71
    name: Get Process Info
    type: splunk
  - id: 3d6c3213-5fff-4a1e-b57d-b24c262171e7
    name: Get Notable History
    type: splunk
  - id: f3fb4d1b-5f33-4b01-b541-c7af9534c242
    name: Get Notable Info
    type: splunk
  - id: fdcfb369-1725-4c24-824a-22972d7f0d65
    name: Get Risk Modifiers For Endpoint
    type: splunk
  - id: bc91a8cf-35e7-4bb2-8140-e756cc06fd74
    name: Get User Information from Identity Table
    type: splunk
  - id: bc91a8cf-35e7-4bb2-8140-e756cc06fd22
    name: Investigate Web Activity From Host
    type: splunk
known_false_positives: Some legitimate applications use long command lines for installs
  or updates. You should review identified command lines for legitimacy. You may modify
  the first part of the search to omit legitimate command lines from consideration.
  If you are seeing more results than desired, you may consider changing the value
  of threshold in the search to a smaller value. You should also periodically re-run
  the support search to re-build the ML model on the latest data. You may get unexpected
  results if the user identified in the results is not present in the data used to
  build the associated model.
maintainers:
  - company: Splunk
    email: rvaldez@splunk.com
    name: Rico Valdez
mappings:
  cis20:
    - CIS 8
  kill_chain_phases:
    - Actions on Objectives
  mitre_attack:
    - Execution
  nist:
    - PR.PT
    - DE.CM
modification_date: '2019-05-08'
name: Unusually Long Command Line - MLTK
original_authors:
  - company: Splunk
    email: rvaldez@splunk.com
    name: Rico Valdez
references: []
security_domain: endpoint
spec_version: 2
type: splunk
version: '1.0'