Microsoft IIS Connection Strings Decryption

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.process-*
logs-windows.forwarded*
logs-windows.sysmon_operational-*
endgame-*
logs-system.security*
logs-m365_defender.event-*
logs-sentinel_one_cloud_funnel.*
logs-crowdstrike.fdr*

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
Data Source: System
Data Source: Microsoft Defender for Endpoint
Data Source: Sysmon
Data Source: SentinelOne
Data Source: Crowdstrike

Version: 312

Rule authors:

Elastic

Rule license: Elastic License v2

Rule query

edit

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&CK^TM

Tactic:
- Name: Credential Access
- ID: TA0006
- Reference URL: https://attack.mitre.org/tactics/TA0006/
Technique:
- Name: OS Credential Dumping
- ID: T1003
- Reference URL: https://attack.mitre.org/techniques/T1003/

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