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Windows IIS connection string decryption via aspnet_regiis -pdf

Flags aspnet_regiis.exe runs that target IIS connectionStrings for decryption using -pdf.

FreeReviewedSigma · High · v2
Product
windows
Category
process_creation
Author
Tim Rauch, Elastic (idea) (SigmaHQ), DRL 1.1
Published
2022-09-28
Updated
2026-07-31
AnalysisDetection

ATT&CK techniques

Cred Access

  1. Recon

  2. Resource Dev

  3. Initial Access

  4. Execution

  5. Persistence

  6. Priv Esc

  7. Defense Evasion

  8. Cred Access

  9. Discovery

  10. Lateral Movement

  11. Collection

  12. C2

  13. Exfiltration

  14. 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

Related detections9 linkedT1003 — drag to rearrange
Malicious Wdigest Authentication Enabled - Reg via Command (via process_creation)
Malicious Diskshadow Command Abuse to Expose VSS Backup (via process_creation)
Malicious IIS Application Pool Credential Dumping (via process_creation)
Malicious Wdigest Authentication Enabled - Registry (via registry_set)
Suspicious Veeam Backup Credential Harvesting via PowerShell (via ps_script)
Suspicious Network Provider Registration for Credential Interception via NPPSpy
Malicious Mimikatz Malicious Security Package (SSP) Exfiltrates Cleartext Passwords in File (via file_event)
Malicious WDigest UseLogonCredential Enablement For Credential Theft
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
  1. v2
    Candidate ingested via manual entry.2026-07-31
  2. 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.