Submon is a simple Bash script designed to monitor live subdomains across multiple target domains.
It uses passive discovery tools and filters the results through httpx, then sends a notification via Discord or Slack when new live subdomains are detected.

• Collects subdomains using:
  • subfinder
  • assetfinder
  • sublist3r
• Filters only live subdomains using httpx
• Tracks newly discovered live subdomains
• Sends alerts via a single WEBHOOK (compatible with Discord or Slack)

Ensure the following tools are installed and accessible from your terminal:

subfinder
assetfinder
sublist3r
httpx
curl

You can install them via package managers like `apt`, `brew`, or from their GitHub repositories.

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## 📁 File Structure

- `submon.sh` → The main script
- `domains.txt` → A text file with one root domain per line
- `submon_data/` → Output directory (auto-created)

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## 📥 Setup

1. **Edit `submon.sh` and set your webhook:**

WEBHOOK="https://discord.com/api/webhooks/..."

or

WEBHOOK="https://hooks.slack.com/services/..."

2. Make the script executable:

chmod +x submon.sh

3. Add your target domains to domains.txt:

example.com
target.org
anotherdomain.net

Run the script manually:

./submon.sh

The script will:

• Discover subdomains from multiple tools
• Check which ones are alive using httpx
• Compare results with previous executions
• Notify you only if new live subdomains are detected

To run it daily, you can create a cronjob:

crontab -e

Add:

@daily /path/to/submon.sh

📡 New live subdomains detected for example.com

• Slack and Discord support is mutually exclusive. You can switch between them by modifying the WEBHOOK variable.

Marcos Suárez (@n31ux)
Security Researcher