Suspicious Antimalware Scan Interface DLL

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Identifies the creation of the Antimalware Scan Interface (AMSI) DLL in an unusual location. This may indicate an attempt to bypass AMSI by loading a rogue AMSI module instead of the legit one.

Rule type: eql

Rule indices:

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

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:

Tags:

  • Elastic
  • Host
  • Windows
  • Threat Detection
  • Defense Evasion
  • Elastic Endgame

Version: 1

Rule authors:

  • Elastic

Rule license: Elastic License v2

Rule query

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file where event.action != "deletion" and file.path != null and
 file.name : ("amsi.dll", "amsi") and not file.path : ("?:\\Windows\\system32\\amsi.dll", "?:\\Windows\\Syswow64\\amsi.dll")

Framework: MITRE ATT&CKTM