How to Fingerprint a Device in Your Local Network Using Python

Light - June 9, 2025, 10:31 a.m.

If you're testing your network or learning ethical reconnaissance, it's often useful to identify what kind of devices are connected to your local network. Rather than just checking if a device is alive, you can actually fingerprint its OS and services using open ports and protocol behaviors.

This guide shows how to write a Python script that:

All in one go.

⚙️ Prerequisites

Install the required Python libraries:

pip install scapy requests impacket

💻 Python Code: Fingerprint a Target by IP

import socket
import requests
from scapy.all import *
from impacket.smbconnection import SMBConnection

def get_os_from_ttl(ip):
    try:
        pkt = IP(dst=ip)/ICMP()
        resp = sr1(pkt, timeout=1, verbose=0)
        if resp:
            ttl = resp.ttl
            if ttl >= 120:
                return f"Windows (TTL={ttl})"
            elif ttl >= 60:
                return f"Linux/Unix (TTL={ttl})"
            elif ttl >= 250:
                return f"Router/IoT (TTL={ttl})"
            else:
                return f"Unknown OS (TTL={ttl})"
        else:
            return "No response"
    except Exception as e:
        return f"Error: {e}"

def grab_banner(ip, port):
    try:
        with socket.socket() as s:
            s.settimeout(2)
            s.connect((ip, port))
            banner = s.recv(1024).decode(errors='ignore').strip()
            return banner if banner else "Empty response"
    except Exception as e:
        return f"Timeout/Error: {e}"

def http_fingerprint(ip):
    try:
        resp = requests.get(f"http://{ip}", timeout=2)
        title = ""
        if "<title>" in resp.text:
            title = resp.text.split("<title>")[1].split("</title>")[0]
        return {
            "status_code": resp.status_code,
            "server": resp.headers.get("Server", "Unknown"),
            "title": title
        }
    except Exception as e:
        return {"error": str(e)}

def get_smb_info(ip):
    try:
        conn = SMBConnection(ip, ip, timeout=2)
        conn.login('', '')  # Anonymous
        return conn.getServerOS()
    except Exception as e:
        return f"SMB error: {e}"

def get_hostname(ip):
    try:
        return socket.gethostbyaddr(ip)[0]
    except:
        return "Unknown"

def scan_target(ip):
    print(f"=== Scanning target: {ip} ===\n")

    print("[*] Hostname:", get_hostname(ip))
    print("[*] OS Guess via TTL:", get_os_from_ttl(ip))
    
    print("\n[*] Banner Grabbing:")
    for port in [22, 445, 80]:
        banner = grab_banner(ip, port)
        print(f"  - Port {port}: {banner}")

    print("\n[*] HTTP Fingerprint:")
    http_info = http_fingerprint(ip)
    for key, value in http_info.items():
        print(f"  {key}: {value}")

    print("\n[*] SMB OS Info (port 445):")
    print(get_smb_info(ip))

if __name__ == "__main__":
    target_ip = input("Enter target IP: ").strip()
    scan_target(target_ip)

🔍 Explanation of Key Techniques

Technique Purpose
ICMP TTL Estimate OS family (Windows/Linux/IoT)
TCP Banner Grabbing Read responses from open ports
HTTP Header Parsing Get web server type & title
SMB OS Retrieval Read OS version from Windows shares
Reverse DNS Lookup Try to resolve hostname

🧪 Sample Output

✅ Use Cases

⚠️ Disclaimer: For Educational Use Only

📌 Legal Notice:
This script is provided strictly for educational and authorized security testing.
Do not use it to probe or fingerprint devices or networks you do not have explicit permission to analyze.
Unauthorized scanning can be illegal and may result in legal penalties.

✅ Always test ethically and within your local laws and guidelines.

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