Microsoft IIS Connection Strings Decryption

SIGMA detection rule by Tim Rauch, Elastic (idea) · NOASSERTION

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.

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

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

6dd14db7-deb5-49ae-bd72-83a86814d1a0

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Executable code, not a declarative rule

This submission is arbitrary [[ currentRule.format ? currentRule.format.toUpperCase() : '' ]] code, not a declarative detection rule — review it as you would any script before running it, and note that it cannot be safely aggregated or auto-executed alongside YARA/Sigma/Suricata/CRS rules.

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Not a security issue — this rule is valid and was accepted as-is. These are optional fields/conventions its own format recommends, mainly affecting its quality score and how well it documents itself for other reviewers.

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[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

[[ currentRule.title ]]

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