huntrule

Windows Registry: Custom URL Protocol Handler Persistence via HKCR\ Protocol Registration

Alerts on HKCR registry set activity registering a new custom URL protocol handler, excluding Microsoft-style ms- protocols.

FreeReviewedSigma · Medium · v1
Product
windows
Category
registry_set
Author
Nasreddine Bencherchali (Nextron Systems) (SigmaHQ), DRL 1.1
Published
2022-05-30
Updated
2026-07-30
AnalysisDetection

ATT&CK techniques

Persistence → Defense Evasion

  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 registry value changes under HKCR where a new custom URL protocol handler is registered (Details starting with "URL:"). Attackers can use custom protocol handlers to persist and trigger execution when users or other software invoke the protocol. It relies on Windows telemetry for registry set events that capture the TargetObject path and the registered Details string, then filters out likely Microsoft protocol registrations ("URL:ms-") and common trusted application locations.

Reporting behind it

Related detections9 linkedT1112 — drag to rearrange
Malicious Enabling of Restricted Admin Mode via Registry by UAT-8837
Suspicious Enabling of Remote Desktop via fDenyTSConnections Registry by DeadLock Ransomware
Malicious Service DLL Hijack for Persistence via Lotus Blossom
Suspicious Loopback Proxy Server Configured via Registry (via registry_set)
Malicious WDigest Credential Caching Enabled via Registry (via registry_set)
Suspicious Remote Desktop Enabled via fDenyTSConnections Registry by Sandworm
Malicious Gh0stBins RAT Registry Marker HHClient
Suspicious PebbleDash C2 Configuration Stored Under WMI Security Key (via registry_set)
Suspicious WDigest UseLogonCredential Enablement for Plaintext Credential Theft (via registry_set)
Windows Registry: Custom URL Protocol Handler Persistence via HKCR\ Protocol Registration
Pivot detection · T1112 · 9 related

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