🔍 ResolverScanner

A tool that finds open DNS resolvers. Give it a list of IP ranges, it sends a DNS question to every IP, and saves the ones that answer correctly.

Iran IPs are already included! The file iran.txt comes with this project and has all Iran IP ranges. You can start scanning right away — no extra setup needed.

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Two Modes

🟢 Open Mode (default)

The scanner sends a DNS question to each IP. If the server sends back any valid DNS answer, it gets saved.

Use this when you just want to find working DNS resolvers in a range of IPs.

🎯 Strict Mode

The scanner sends a DNS question. But this time, it only saves servers that return a specific IP address you tell it to look for.

Why would you use this?

Imagine you run a VPN or a website. Your domain vpn.example.com points to your server IP 1.2.3.4.

You want to find DNS servers (for example, in Iran) that give back the real answer for your domain — not a fake or blocked one.

You run:

python dns_scanner.py --expected-ip 1.2.3.4

Now the scanner only saves DNS servers that return 1.2.3.4. This means those servers are not censored and have not been tampered with. Servers that return a wrong IP (or no IP) are ignored.

Think of it as a filter: only the "clean" DNS servers pass through. ✅

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Requirements

• Python 3.10 or newer
• No extra packages needed — uses only built-in Python tools

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Quick Start

1. The Iran IP file is already there — iran.txt is included with all Iran IP ranges. Nothing to download.

2. Run the scanner:

   python dns_scanner.py
   

3. See results in found_resolvers.txt

That's it! 🎉

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Usage

python dns_scanner.py [OPTIONS]

Options

Flag	Default	Description
--cidr-file	iran.txt	File with IP ranges to scan
--domain	example.com	The domain name to ask about
--expected-ip	(none)	Only save servers that return this IP (strict mode)
--ports	53	Port numbers to scan (separate with commas)
--timeout	3.0	How many seconds to wait for a reply
--concurrency	2000	How many IPs to check at the same time
--sockets	50	Number of UDP sockets to use
--output	found_resolvers.txt	File to save results in

Examples

Find all open resolvers (default — uses iran.txt):

python dns_scanner.py

Strict mode — only resolvers that return a specific IP:

python dns_scanner.py --expected-ip 1.2.3.4

Scan extra ports:

python dns_scanner.py --ports 53,5353,8053

Use a different IP list file:

python dns_scanner.py --cidr-file my_ranges.txt --output my_results.txt

Faster scan (more sockets and workers, shorter wait time):

python dns_scanner.py --sockets 100 --concurrency 3000 --timeout 1.0

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IP File Format

One IP range (or single IP) per line. Lines that start with # are skipped (comments).

# This is a comment
192.168.0.0/24
10.0.0.0/16
8.8.8.8

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Output

Results are saved as IP:PORT, one per line:

1.2.3.4:53
5.6.7.8:53