Windows IIS connection string decryption via aspnet_regiis -pdf

ATT&CK techniques

Cred Access

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
- T1003OS Credential Dumping
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags execution of aspnet_regiis.exe with arguments indicating connectionStrings decryption and PDF output. Attackers who gain IIS server access can use this functionality to extract or decrypt hardcoded connection strings, potentially including sensitive credentials. It relies on Windows process creation telemetry capturing the process image and command-line arguments.

Reporting behind it

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Linux: Detect changes to fs.suid_dumpable enabling core dumps for SUID processes

Windows IIS connection string decryption via aspnet_regiis -pdf

Pivot detection · T1003 · 9 related

Changelog

v2

v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

windows-iis-aspnet-regiis-decrypts-connection-strings-via-pdf-97dbf6e2

title: Windows IIS connection string decryption via aspnet_regiis -pdf
id: 10ed6362-ac56-4fa2-85ec-100928981b6d
status: test
description: This rule flags execution of aspnet_regiis.exe with arguments indicating connectionStrings decryption and PDF output. Attackers who gain IIS server access can use this functionality to extract or decrypt hardcoded connection strings, potentially including sensitive credentials. It relies on Windows process creation telemetry capturing the process image and command-line arguments.
references:
  - https://www.elastic.co/guide/en/security/current/microsoft-iis-connection-strings-decryption.html
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_iis_connection_strings_decryption.yml
author: Tim Rauch, Elastic (idea), Huntrule Team
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
license: DRL-1.1
related:
  - id: 97dbf6e2-e436-44d8-abee-4261b24d3e41
    type: derived

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