How to Set Up a Raspberry Pi Network Scanner?

A network scanner allows you to discover all the devices connected to your local network. This can help identify intruders, troubleshoot connectivity issues, and map your network infrastructure.

How to Set Up a Raspberry Pi Network Scanner?

The Raspberry Pi is an inexpensive, yet surprisingly capable, single-board computer that is perfect for building a network scanner. With just a few commands and some free software, you can set up a Raspberry Pi to regularly scan your network and report back all connected devices.

Benefits

Some key benefits of setting up a Raspberry Pi network scanner include:

  • Low Cost: The Raspberry Pi and required accessories cost less than $100. Much cheaper than buying an enterprise network scanner.
  • Customizable: You can customize the scan frequency, depth, and retention time of logs. Tailor it to your needs.
  • Compact: The entire scanner fits in the palm of your hand. You can place it anywhere on your network.
  • Educational: Learn skills like network scanning, Linux administration, scripting, logging, and security auditing.

Prerequisites

Before getting started with setting up a Raspberry Pi network scanner, you’ll need the following:

Hardware

  • Raspberry Pi computer
  • SD Card with Raspbian OS preloaded
  • Power adapter
  • Network cable

Software

  • Latest version of Nmap network scanning tool
  • Bash shell scripting basics

Networking Knowledge

  • Understanding of IP addresses, subnets, and port numbers
  • Familiar with network topology and connected devices
  • Know where to place the Raspberry Pi on the network for best visibility

Installation and Configuration

Follow these steps to install and configure your Raspberry Pi network scanner:

Step 1 — Set Up the Raspberry Pi

First, connect the Raspberry Pi to your network router via an ethernet cable, attach the power adapter, insert the SD card, and power it on. Log into the Raspberry Pi desktop.

Step 2 — Install Updates and Nmap

Open a terminal window and run the following commands one by one to install updates and Nmap network scanning tool:

sudo apt update

sudo apt full-upgrade

sudo apt install nmap

Step 3 — Create Custom Nmap Scanning Script

With Nmap installed, create an Nmap scanning bash script file in your preferred text editor. Here are some key script features to include:

  • Specify Network: Set the target network IP address range to scan
  • Scan Frequency: Set scanning interval to run regularly, e.g. every hour
  • Output File: Log results to a local file, e.g. scanlog.txt
  • Custom Flags: Specify custom Nmap command flags like -sP for ping scan

Example Script:

#!/bin/bash

# Set target subnet  

SUBNET=192.168.1.0/24

 Schedule scan interval  

while :

do

      Run scan

     nmap -sP $SUBNET

      Redirect output 

     nmap … >> /home/pi/scanlog.txt

      Set interval 

     sleep 1h  

done

Step 4 — Make the Script Executable

Save your Nmap scanning script then run the following command to make it executable:

sudo chmod +x ~/network-scan.sh

Step 5 — Test It Out!

Execute your script to confirm that it runs without errors and logs results successfully after each scan interval:

sudo ./network-scan.sh

Check your scanlog.txt file after a few minutes to ensure new hosts on your network are being discovered and logged properly.

Remote Monitoring

With the scanner running smoothly on your Raspberry Pi, there are a couple options to access the logs remotely:

Method 1 — Use Built-In Raspberry Pi Tools

You can remotely log into the Raspberry Pi using SSH or VNC and view the real time logs of your Nmap scanner. Use the Raspberry Pi IP address to connect another machine using SSH or VNC client software.

Method 2 — Send Logs to Central Server

Edit your Nmap script on the Pi to send a copy of the scan logs file after each run using SCP to a central syslog server or monitoring server of your choice. This keeps an archive of logs for easier long term review.

Additional Customizations

Some additional features you can add to your Raspberry Pi network scanner include:

  • Email scan result alerts to your inbox
  • Create a web dashboard showing a list of devices
  • Scan specific ports for vulnerabilities
  • Compare historical scans for new devices
  • Automate identification of rogue devices

The possibilities are endless for building on your Raspberry Pi network scanner!

Troubleshooting Common Issues

Here are some common issues and fixes for your Raspberry Pi network scanning tool:

Problem: Nmap not running successfully

Solution: Update Nmap to the latest version or use sudo to allow necessary permissions

Problem: Can’t access Raspberry Pi over network

Solution: Check IP configuration is correct. Verify connection with ping raspberrypi.local

Problem: Scan logs show nothing discovered

Solution: Check IP range covers your full network subnet. Review Nmap flags used

Conclusion

Setting up a DIY Raspberry Pi network scanner is a fun and educational project that can provide real value monitoring dubious activity on your local network. With just the Pi hardware, Nmap software, and a custom script you can easily automate discovery and logging of all devices connecting to your network. You also get flexibility to customize scans to suit exactly what information you want to surface.

Frequently Asked Questions

  1. What are the benefits of building your own Pi Network Scanner vs buying one?
    Building your own Raspberry Pi Network Scanner is extremely cost-effective compared to buying enterprise hardware appliances or services. It also lets you customize features tailored to your needs.

  2. Do I need coding skills to set this up?
    Some basic Linux and scripting knowledge helps but is not necessary. Our guide has all the key pieces you can copy to build your scanner without needing to code anything from scratch.

  3. What hardware accessories do I need alongside the Raspberry Pi?
    You’ll need a microSD card preloaded with the Raspbian operating system, a power supply, and an ethernet cable for connecting the Pi to your home network router.

  4. Can I power the Pi over ethernet?
    Yes, many modern ethernet switches and routers supply Power over Ethernet which lets you power your Raspberry Pi through the network cable without needing a separate micro USB adapter.

  5. What is the scan output logged to?
    Our guide saves all scan results to a local text file named scanlog.txt on the Raspberry Pi itself. You can optionally configure the Pi to send these logs to a remote central server.

  6. Can I access the logs from my desktop PC?
    Yes! You can remotely log in to your Raspberry Pi using SSH or remote desktop software like VNC viewer and directly view the latest logs in real time.

  7. How often does Nmap run scans?
    Our script has Nmap scans configured to run once per hour. But this interval can be easily customized by changing the sleep delay. Scanning too frequently may have performance impacts.

  8. Will this identify network intrusions?
    While primarily useful for inventorying devices, comparing historical scans can help flag new unknown devices connecting to your network without permission. Frequent scans increase this capability.

  9. Can I scan my neighbor’s Wi-Fi networks?
    Scanning external networks without permission crosses ethical and legal boundaries in most regions. Restrict your Nmap scans only to networks and devices you own or have permission to analyze.

  10. Does Nmap have any destructive abilities?
    Nmap is designed to be safe and non-destructive during scans. But before scanning any production networks, first test in a safe isolated test environment.

  11. What does the -sP flag used in the Nmap script do?
    The -sP flag configures Nmap to do a simple ping scan, which swiftly discovers all online hosts without probing deeper into services and ports running on each device.

  12. Can I modify the script to scan at random times?
    Yes, the script logic could be updated to trigger scans at random intervals rather than on a fixed static schedule. This adds variability and complexity useful for certain contexts.

  13. How do I save Nmap output to Elasticsearch?
    You can parse the raw Nmap output and convert to JSON documents that get indexed directly into an Elasticsearch cluster for search and visualization.

  14. What type of Raspberry Pi do I need?
    Any model of Raspberry Pi will work fine for this project, but newer generation models like Raspberry Pi 4 have faster processor and networking performance for quicker scans.

  15. Can I connect sensors to detect network intruders physically?
    Yes! For advanced projects, you could add physical entry sensors or motion detectors that automatically trigger network scans whenever doors open or movement occurs around server racks.

  16. What other scan options does Nmap provide?
    Nmap has over 100 advanced options for specialized scan types like DNS lookups, operating system fingerprinting, service detection, script scanning, traceroute and many more for researching device details.

  17. Can I monitor scans and alerts through a mobile app?
    Yes, there are great platforms like Nagios and Zabbix that let you build mobile apps with push notifications triggered by your Pi scanning key events like new devices discovered.

  18. Can I make the Raspberry Pi mobile to scan different locations?
    Yes, you can set up the Pi with a battery pack and small monitor to create a mobile network scanning device. This lets you easily plug it in and scan different parts of your network by location.

  19. What kind of usage patterns should I expect on the SD card from frequent scanning?
    With a scan interval of 1 hour, the SD card should handle this workload easily for well over 12 months before needing replacement. Use brand name high-endurance SD cards for best reliability.

  20. Is it possible to confuse an Nmap scan by changing device MAC addresses?
    Network devices can be configured to dynamically alter their MAC address with randomization or spoofing. But Nmap has options like the -R flag to help cut through attempts at scan evasion using such techniques.

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