Microsoft IIS Connection Strings Decryption — Sigma Rule

Rule metadata and linked tags

Author: Tim Rauch, Elastic (idea). Source status: test; severity: high. Source dates: 2022-09-28 / 2022-12-30.

{
  "category": "process_creation",
  "product": "windows"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 3b8eebfa541aab0fd8f4875f8472b5d39a9ef1a7e7b7eef8b7e0cd32d2765518

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Microsoft IIS Connection Strings Decryption
id: 97dbf6e2-e436-44d8-abee-4261b24d3e41
status: test
description: Detects 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.
references:
    - https://www.elastic.co/guide/en/security/current/microsoft-iis-connection-strings-decryption.html
author: Tim Rauch, Elastic (idea)
date: 2022-09-28
modified: 2022-12-30
tags:
    - attack.credential-access
    - attack.t1003
logsource:
    category: process_creation
    product: windows
detection:
    selection_name:
        - Image|endswith: '\aspnet_regiis.exe'
        - OriginalFileName: 'aspnet_regiis.exe'
    selection_args:
        CommandLine|contains|all:
            - 'connectionStrings'
            - ' -pdf'
    condition: all of selection*
falsepositives:
    - Unknown
level: high

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• https://www.elastic.co/guide/en/security/current/microsoft-iis-connection-strings-decryption.html