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Suspicious Execution from a Mounted Device

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Suspicious Execution from a Mounted Device

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Identifies when a script interpreter or signed binary is launched via a non-standard working directory. An attacker may use this technique to evade defenses.

Rule type: eql

Rule indices:

  • winlogbeat-*
  • logs-endpoint.events.process-*
  • logs-windows.sysmon_operational-*

Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

Tags:

  • Domain: Endpoint
  • OS: Windows
  • Use Case: Threat Detection
  • Tactic: Defense Evasion
  • Tactic: Execution
  • Data Source: Elastic Defend
  • Data Source: Sysmon

Version: 208

Rule authors:

  • Elastic

Rule license: Elastic License v2

Setup

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Setup

If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2, events will not define event.ingested and default fallback for EQL rules was not added until version 8.2. Hence for this rule to work effectively, users will need to add a custom ingest pipeline to populate event.ingested to @timestamp. For more details on adding a custom ingest pipeline refer - https://www.elastic.co/guide/en/fleet/current/data-streams-pipeline-tutorial.html

Rule query

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process where host.os.type == "windows" and event.type == "start" and process.executable : "C:\\*" and
  (process.working_directory : "?:\\" and not process.working_directory: "C:\\") and
  process.parent.name : "explorer.exe" and
  process.name : ("rundll32.exe", "mshta.exe", "powershell.exe", "pwsh.exe", "cmd.exe", "regsvr32.exe",
                  "cscript.exe", "wscript.exe")

Framework: MITRE ATT&CKTM

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