IMPORTANT: No additional bug fixes or documentation updates will be released for this version. For the latest information, see the current release documentation.

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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.*
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: 107

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&CK^TM

Tactic:
- Name: Defense Evasion
- ID: TA0005
- Reference URL: https://attack.mitre.org/tactics/TA0005/
Technique:
- Name: System Binary Proxy Execution
- ID: T1218
- Reference URL: https://attack.mitre.org/techniques/T1218/
Sub-technique:
- Name: Mshta
- ID: T1218.005
- Reference URL: https://attack.mitre.org/techniques/T1218/005/
Sub-technique:
- Name: Regsvr32
- ID: T1218.010
- Reference URL: https://attack.mitre.org/techniques/T1218/010/
Sub-technique:
- Name: Rundll32
- ID: T1218.011
- Reference URL: https://attack.mitre.org/techniques/T1218/011/
Tactic:
- Name: Execution
- ID: TA0002
- Reference URL: https://attack.mitre.org/tactics/TA0002/
Technique:
- Name: Command and Scripting Interpreter
- ID: T1059
- Reference URL: https://attack.mitre.org/techniques/T1059/
Sub-technique:
- Name: PowerShell
- ID: T1059.001
- Reference URL: https://attack.mitre.org/techniques/T1059/001/
Sub-technique:
- Name: Windows Command Shell
- ID: T1059.003
- Reference URL: https://attack.mitre.org/techniques/T1059/003/

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