Microsoft IIS Connection Strings Decryptionedit

Identifies use of aspnet_regiis to decrypt Microsoft IIS connection strings. An attacker with Microsoft IIS web server access via a webshell or alike can decrypt and dump any hardcoded connection strings, such as the MSSQL service account password using aspnet_regiis command.

Rule type: eql

Rule indices:

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

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: 33

References:

Tags:

  • Domain: Endpoint
  • OS: Windows
  • Use Case: Threat Detection
  • Tactic: Credential Access
  • Data Source: Elastic Endgame
  • Data Source: Elastic Defend

Version: 109

Rule authors:

  • Elastic

Rule license: Elastic License v2

Setupedit

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 queryedit

process where host.os.type == "windows" and event.type == "start" and
  (process.name : "aspnet_regiis.exe" or ?process.pe.original_file_name == "aspnet_regiis.exe") and
  process.args : "connectionStrings" and process.args : "-pdf"

Framework: MITRE ATT&CKTM