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d1vious
88 lines
3.7 KiB
YAML
88 lines
3.7 KiB
YAML
author: Ignacio Bermudez Corrales, Splunk
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datamodel:
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- Endpoint_Processes
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date: '2020-10-06'
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description: Command lines that are extremely long may be indicative of malicious
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activity on your hosts. This search leverages the Splunk Streaming ML DSP plugin
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to help identify command lines with lengths that are unusual for a given user. This
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detection is inspired on Unusually Long Command Line authored by Rico Valdez.
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how_to_implement: You must be ingesting sysmon endpoint data that monitors command
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lines.
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id: 58f43aba-1775-445e-b19c-be2b87d83ae3
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known_false_positives: This detection may flag suspiciously long command lines when
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there is not sufficient evidence (samples) for a given process that this detection
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is tracking; or when there is high variability in the length of the command line
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for the tracked process. Also, some legitimate applications may use long command
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lines. Such is the case of Ansible, that encodes Powershell scripts using long base64.
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Attackers may use this technique to obfuscate their payloads.
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name: Unusually Long Command Line
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product:
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- Splunk Behavioral Analytics
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references: []
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risk_message: A process $process_name$ with a long commandline $cmd_line$ executed
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in host $dest_device_id$
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search: ' | from read_ssa_enriched_events() | eval timestamp=parse_long(ucast(map_get(input_event,
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"_time"), "string", null)) | eval cmd_line=ucast(map_get(input_event, "process"),
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"string", null), dest_user_id=ucast(map_get(input_event, "dest_user_id"), "string",
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null), dest_device_id=ucast(map_get(input_event, "dest_device_id"), "string", null),
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process_name=ucast(map_get(input_event, "process_name"), "string", null), event_id=ucast(map_get(input_event,
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"event_id"), "string", null) | where cmd_line!=null and dest_user_id!=null | eval
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cmd_line_norm=replace(cast(cmd_line, "string"), /\s(--?\w+)|(\/\w+)/, " ARG"), cmd_line_norm=replace(cmd_line_norm,
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/\w:\\[^\s]+/, "PATH"), cmd_line_norm=replace(cmd_line_norm, /\d+/, "N"), input=parse_double(len(coalesce(cmd_line_norm,
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""))) | select timestamp, process_name, dest_device_id, dest_user_id, cmd_line,
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input | adaptive_threshold algorithm="quantile" entity="process_name" window=60480000
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| where label AND quantile>0.99 | first_time_event input_columns=["dest_device_id",
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"cmd_line"] | where first_time_dest_device_id_cmd_line | eval start_time = timestamp,
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end_time = timestamp, entities = mvappend(dest_device_id, dest_user_id), body=create_map(["event_id",
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event_id, "cmd_line", cmd_line, "process_name", process_name]) | into write_ssa_detected_events();'
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tags:
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analytic_story:
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- Unusual Processes
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cis20:
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- CIS 8
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confidence: 40
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context:
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- source:endpoint
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- stage: Defense Evasion
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impact: 30
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kill_chain_phases:
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- Actions on Objectives
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message: A process $process_name$ with a long commandline $cmd_line$ executed in
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host $dest_device_id$
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nist:
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- PR.PT
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- DE.CM
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observable:
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- name: dest_device_id
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role:
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- Victim
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type: Hostname
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- name: dest_user_id
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role:
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- Victim
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type: user
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product:
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- Splunk Behavioral Analytics
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required_fields:
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- process_name
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- _time
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- dest_device_id
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- dest_user_id
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- process
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risk_score: 12
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risk_severity: medium
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security_domain: endpoint
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test:
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name: Unusually Long Command Line - SSA Unit Test
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tests:
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- attack_data:
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- data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1059.003/unusally_cmd_line/windows-security.log
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file_name: windows-security.log
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source: WinEventLog:Security
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description: Test unusually long command lines
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file: endpoint/ssa___unusually_long_command_line.yml
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name: Unusually Long Command Line
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pass_condition: '@count_gt(0)'
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type: Anomaly
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version: 1
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