CT Monitor Runtime

Real-time Certificate Transparency log monitoring

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About

The Certificate Transparency Real-Time Monitor watches CT logs for newly issued certificates matching your domain patterns, providing immediate visibility into certificate issuance across all Certificate Authorities. It uses the Certificate Transparency protocol to detect unauthorized certificate issuance, track CA behavior, and ensure no certificates are issued without your knowledge.

CT monitoring is a critical security control that complements traditional certificate management. Even if you control your primary certificate issuance process, certificates can be issued by other CAs (with or without authorization). Real-time CT monitoring catches these events immediately, whether they represent legitimate multi-CA strategies, vendor-issued certificates, or unauthorized issuance attempts.

How to Use

1Enter domain patterns to monitor (exact domains or wildcard patterns)
2Configure the monitoring frequency (real-time, hourly, or daily)
3The system continuously queries CT logs for matching certificates
4Receive alerts when new certificates are detected matching your patterns

Use Cases

•Unauthorized Issuance Detection: Immediately detect certificates issued for your domains by CAs you did not authorize, preventing potential phishing or MITM attacks
•CA Monitoring: Track all certificate issuance across your organization including certificates issued by managed CAs, CDN providers, and cloud services
•Phishing Detection: Detect certificates issued for domains similar to yours that could be used for phishing campaigns
•Compliance Evidence: Document CT monitoring as evidence of certificate lifecycle management for PCI DSS and SOC 2 audits
•Vendor Visibility:** Gain visibility into certificates issued by third-party vendors that manage certificates on your behalf

What The Search Covers

Certificate Transparency logs record every publicly trusted issuance permanently. This page queries an aggregated index for a domain and reports what has been issued.

1Query the aggregated search index for the domain and read the entries it returns — common name, issuer, validity window, serial and the log that recorded each.

2Count what was found, because the total is the interesting signal. A count beyond what your estate should have issued suggests someone else obtained certificates for your domain, which is the misissuance case transparency exists to make visible.

3Report query failure as failure. An unreachable index and a domain with no certificates look identical otherwise, and confusing the two leads to false confidence in the second case.

Results come from an aggregated index rather than an individual log, so coverage and ordering belong to that service. Verifying that a specific certificate is in a specific log means querying the log directly, which is what proper monitoring should do.

Tips & Best Practices

•Monitor both exact domains and common misspellings (typosquatting patterns)

•Set up real-time alerts for high-value domains and daily summaries for lower-priority domains

•Combine CT monitoring with fingerprint monitoring for complete certificate change detection

•Use wildcard patterns to catch subdomains you may not be directly tracking

Technical Details

●CT Log Sources: Google Argon, Cloudflare Nimbus, DigiCert Yeti, and other participating CT logs

●Search Methods: Exact domain match, wildcard pattern, regex domain matching, and similar-domain detection

●Latency: Real-time mode detects certificates within minutes of CT log submission

●API Integration: Webhook and REST API for automated alerting and response workflows

Frequently Asked Questions

Certificate Transparency (CT) is a system that requires CAs to log all issued certificates in public, append-only logs. This creates a verifiable record of certificate issuance that domain owners can monitor. CT was developed by Google and is now required by all major browsers for SSL certificates.

In real-time mode, certificates are typically detected within 5-15 minutes of issuance. Most CAs submit to CT logs within minutes of certificate issuance. The monitoring system queries logs every 5 minutes in real-time mode, every hour in standard mode, and daily in summary mode.

Yes, you can monitor any domain pattern including domains similar to yours (for phishing detection), competitor domains (for market intelligence), or domains in your industry (for threat awareness). This is useful for detecting certificates issued for typosquatting or brand impersonation.

Continuously, if you rely on CT for misissuance detection, because the window between a certificate being issued and your noticing is the window an attacker has. Automated monitoring against your domains is the intended use; checking manually finds problems eventually rather than promptly. For a small estate a weekly check catches most real cases, since misissued certificates for a domain tend to accumulate rather than appear and vanish.

Usually benign and worth understanding rather than alarming. Wildcards, short-lived issuance and multiple environments all produce more entries than you may have issued deliberately, and older certificates persist in the logs after you have moved on. What matters is whether every entry is one you can account for. Ones you cannot explain are the finding, and the right response is to contact the authority and have them revoked.

No. Only certificates from publicly trusted authorities are required to log, so anything from a corporate or private CA will not appear. A domain showing nothing may therefore be using internal PKI rather than having a transparency problem. That distinction matters when monitoring — an empty result means only that nothing public was issued, not that nothing exists.

Not on their own. Logs are append-only and permanent by design, so every certificate ever issued for your domain is there forever, including ones long since expired and replaced. The permanence is the feature, not a problem. What matters is the current state and whether any unrecognised entry was ever validly issued and left unrevoked.

Different questions entirely. This searches the historical record of what was issued for a domain; a live check tells you what one host is serving right now. Both are needed: transparency finds issuance you did not request, while a live check finds misconfiguration on servers you do control. Neither substitutes for the other.

Related Tools

CT Monitor CT Feed CT Search CT Log Certificate Detail Issuer Identifier