crtmon

[!NOTE] crtmon is a lightweight Certificate Transparency monitoring tool that discovers new subdomains in real time as soon as they appear.

Features

• Real-time subdomain discovery from CT logs
• Discord and Telegram notifications
• Smart batching with built-in rate limiting
• Supports single targets, files, and stdin

Installation

go install github.com/coffinxp/crtmon@latest

Configuration

Run crtmon once to generate the default configuration template:

crtmon

Edit the generated file:

~/.config/crtmon/provider.yaml

Flags

-target    target domain, file path, or '-' for stdin
-config    path to configuration file (default: ~/.config/crtmon/provider.yaml)
-notify    notification provider: discord, telegram, both
-version   show version
-update    update to latest version
-h, -help  show help message

Usage Examples

• Monitor a single target

crtmon -target github.com

• Monitor targets from config file

crtmon # config: ~/.config/crtmon/provider.yaml

• Monitor multiple targets from a file

crtmon -target targets.txt

• Pipe targets via stdin

cat domains.txt | crtmon -target -

• Use Telegram notifications only

crtmon -target github.com -notify telegram

• Dual notifications (Discord + Telegram)

echo -e "tesla.com\nuber.com\nmeta.com" | crtmon -target - -notify both

• Start on system reboot (cron)

echo "@reboot nohup crtmon -target github.com > /tmp/crtmon.log 2>&1 &" | crontab -

[!TIP]

If you see no output or errors:

• Verify your targets are valid
• Double check notification credentials
• Ensure Docker is installed and running
• Check your internet connection
• Run crtmon -h for guidance

TO-DO

• Separate notification channels per target

[!CAUTION] Use crtmon only on assets you own or have permission to test. The authors are not responsible for misuse...