splunk-security_content/detections/malicious_powershell_process_obfuscation_techniques.json

{
  "asset_type": "Endpoint",
  "confidence": "medium",
  "creation_date": "2017-04-25",
  "data_metadata": {
    "data_models": [
      "Endpoint"
    ],
    "data_source": [
      "Endpoint Intel"
    ],
    "providing_technologies": [
      "Carbon Black Response",
      "CrowdStrike Falcon",
      "Sysmon",
      "Tanium",
      "Ziften"
    ]
  },
  "description": "This search looks for PowerShell processes launched with arguments that have characters indicative of obfuscation on the command-line.",
  "detect": {
    "splunk": {
      "correlation_rule": {
        "notable": {
          "nes_fields": "dest, user, process_name, process",
          "rule_description": "The system $dest$ executed a PowerShell process that has evidence of obfuscation on the command-line",
          "rule_title": "PowerShell process with an obfuscation techniques detected on $dest$"
        },
        "risk": {
          "risk_object": "dest",
          "risk_object_type": [
            "system"
          ],
          "risk_score": 60
        },
        "schedule": {
          "cron_schedule": "0 * * * *",
          "earliest_time": "-70m@m",
          "latest_time": "-10m@m"
        },
        "search": "| tstats `summariesonly` count values(Processes.process) as process values(Processes.parent_process) as parent_process min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.process_name=powershell.exe by Processes.user Processes.process_name Processes.parent_process_name Processes.dest  | `drop_dm_object_name(Processes)` | `ctime(firstTime)`| `ctime(lastTime)`| eval num_obfuscation = (mvcount(split(process, \"`\"))-1) + (mvcount(split(process, \"^\"))-1) | search num_obfuscation > 0",
        "suppress": {
          "suppress_fields": "dest,process_name,process",
          "suppress_period": "14400s"
        }
      }
    }
  },
  "eli5": "This search looks for PowerShell processes that are passing command-line arguments with unusual characters (backticks and carets) that are PowerShell specific escape characters. Attackers use this obfuscation technique since it does not affect the functionality of PowerShell and it will bypass standard security controls that look for straight up malicious strings and commands. The search counts the occurrence of these obfuscation characters and lists out destination IPs running these PowerShell commands.",
  "entities": [
    "dest"
  ],
  "how_to_implement": "You must be ingesting data that records process activity from your hosts to populate the Endpoint data model in the Processes node. You must also be ingesting logs with both the process name and command line from your endpoints. The command-line arguments are mapped to the \"process\" field in the Endpoint data model.",
  "id": "cde75cf6-3c7a-4dd6-af01-27cdb4511fd4",
  "investigations": [
    {
      "id": "bc91a8cf-35e7-4bb2-8140-e756cc06fd76",
      "name": "Get Authentication Logs For Endpoint",
      "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"
    }
  ],
  "known_false_positives": "These characters might be legitimately on the command-line, but it is not common.",
  "maintainers": [
    {
      "company": "Splunk",
      "email": "davidd@splunk.com",
      "name": "David Dorsey"
    }
  ],
  "mappings": {
    "cis20": [
      "CIS 3",
      "CIS 7",
      "CIS 8"
    ],
    "kill_chain_phases": [
      "Command and Control",
      "Actions on Objectives"
    ],
    "mitre_attack": [
      "Execution",
      "PowerShell",
      "Scripting"
    ],
    "nist": [
      "PR.PT",
      "DE.CM",
      "PR.IP"
    ]
  },
  "modification_date": "2018-12-03",
  "name": "Malicious PowerShell Process With Obfuscation Techniques",
  "original_authors": [
    {
      "company": "Splunk",
      "email": "davidd@splunk.com",
      "name": "David Dorsey"
    }
  ],
  "references": [],
  "security_domain": "endpoint",
  "spec_version": 2,
  "type": "splunk",
  "version": "2.0"
}