Introduction

In bug bounty hunting, timing matters. By the time a new subdomain is picked up by automated scanners, public wordlists, or program scope updates, it has usually already been tested by others. The real advantage comes from discovering assets the moment they are created. That’s where Certificate Transparency monitoring helps. In this guide, I’ll show you how to use crtmon to watch CT logs in real time and get alerts as soon as new subdomains are issued, running 24/7 so you don’t miss anything even while you sleep.

Why Monitor Certificate Transparency?

Whenever a CA (Certificate Authority) issues an SSL/TLS certificate for a domain, it must be logged in a public Certificate Transparency log.

By monitoring these logs, you can:

• Discover “Fresh” Assets: Test subdomains minutes after they are created.
• Avoid Duplicates: Find bugs before they are reported by hunters using static datasets.
• Automate Recon: Let the tool do the heavy lifting while you focus on manual testing.