Unusual Executable File Creation by a System Critical Process

Identifies an unexpected executable file being created or modified by a Windows system critical process, which may indicate activity related to remote code execution or other forms of exploitation.

Rule type: eql

Rule indices:

winlogbeat-*
logs-endpoint.events.*
logs-windows.*

Severity: high

Risk score: 73

Runs every: 5m

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

Maximum alerts per execution: 100

References: None

Tags:

Elastic
Host
Windows
Threat Detection
Defense Evasion

Version: 5

Rule authors:

Elastic

Rule license: Elastic License v2

Investigation guide

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## Config

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 8.2, so you will need to add a custom pipeline to populate `event.ingested` to @timestamp for this rule to work.

Rule query

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file where event.type != "deletion" and
  file.extension : ("exe", "dll") and
  process.name : ("smss.exe",
                  "autochk.exe",
                  "csrss.exe",
                  "wininit.exe",
                  "services.exe",
                  "lsass.exe",
                  "winlogon.exe",
                  "userinit.exe",
                  "LogonUI.exe")

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Defense Evasion
- ID: TA0005
- Reference URL: https://attack.mitre.org/tactics/TA0005/
Technique:
- Name: Exploitation for Defense Evasion
- ID: T1211
- Reference URL: https://attack.mitre.org/techniques/T1211/

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