Unusual Web Config File Access

Last updated 15 days ago on 2026-01-19

Created 6 months ago on 2025-07-23

About

Detects unusual access to the web.config file, which contains sensitive credential information such as database connection strings, machineKey validation/decryption keys, and SAML/OAuth token settings. Attackers can use the information extracted to forge malicious __VIEWSTATE requests for persistent RCE on the web server or pivot to the SQL server using exposed connection strings.

Tags

Domain: EndpointOS: WindowsUse Case: Threat DetectionTactic: Credential AccessData Source: Elastic DefendLanguage: kuery

Severity

high

Risk Score

MITRE ATT&CK™

Credential Access (TA0006)(external, opens in a new tab or window)

↳ OS Credential Dumping (T1003)(external, opens in a new tab or window)

License

Elastic License v2(external, opens in a new tab or window)

Definition

Rule Type: New Terms Rule
Integration Pack: Prebuilt Security Detection Rules
Index Patterns: logs-endpoint.events.file-*
Related Integrations: endpoint(external, opens in a new tab or window)
Query

✄𐘗text code block:
✄𐘗event.category:file and host.os.type:windows and event.action:open and
  file.name:"web.config" and file.path : *VirtualDirectories* and
  not process.executable: (
        "C:\Program Files\Microsoft Security Client\MsMpEng.exe" or
        "C:\Program Files\Windows Defender Advanced Threat Protection\MsSense.exe" or
        "C:\Windows\System32\MRT.exe"
  )

Install detection rules in Elastic Security

Detect Unusual Web Config File Access in the Elastic Security detection engine by installing this rule into your Elastic Stack.

To setup this rule, check out the installation guide for Prebuilt Security Detection Rules(external, opens in a new tab or window).