Uncovering the hidden treasures of your Raspberry Pi with nmap

Learn how to check open ports on a Raspberry Pi using nmap and what it means for security. …

Updated October 27, 2023

Learn how to check open ports on a Raspberry Pi using nmap and what it means for security.

As a Raspberry Pi enthusiast, you’ve probably heard about network scanning tools like nmap (Network Mapper). These tools are used by hackers to scan networks and identify vulnerable systems. However, they can also be used by system administrators and penetration testers to audit their networks for security weaknesses. In this article, we will show you how to use nmap to check open ports on your Raspberry Pi and understand the implications of having open ports for your device’s security.

What are Open Ports?

Ports are like doors that allow communication between two devices over a network. They are identified by a unique number, and they can be either open or closed. When a port is open, it means it allows data to pass through, while a closed port blocks all incoming connections. In the context of Raspberry Pi, open ports could be potential security risks as attackers may exploit them to gain unauthorized access to your device.

Installing nmap on Raspberry Pi

Before you can use nmap, you need to install it on your Raspberry Pi. Open a terminal and run the following commands:

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install nmap

This will download and install the latest version of nmap on your Raspberry Pi.

Scanning Open Ports with nmap

To scan open ports on your Raspberry Pi, you can use the following command:

nmap -p- <IP address or hostname>

Replace <IP address or hostname> with either the IP address or the hostname of your Raspberry Pi. For example:

nmap -p- 192.168.1.100

nmap -p- raspberrypi.local

This command will scan all ports on the specified IP address or hostname and report which ones are open. The output will look something like this:

Starting Nmap 7.91 ( https://nmap.org ) at 2022-03-14 12:00 UTC
Nmap scan report for raspberrypi.local (192.168.1.100)
Host is up (0.000027s latency).
Not shown: 995 closed ports
PORT     STATE SERVICE
22/tcp   open  ssh
80/tcp   open  http
443/tcp  open  https
3389/tcp open  ldap
88/tcp   open  kerberos-sec
Nmap done: 1 IP address (1 host up) scanned in 2.57 seconds

In this example, we can see that ports 22, 80, 443, 389 and 88 are open on the Raspberry Pi. These ports could be used by attackers to exploit vulnerabilities or perform unauthorized actions.

Interpreting nmap Output

The output of the nmap command can be a bit overwhelming at first, but it’s not as complicated as it seems. Here’s what each line means:

The first line shows that Nmap has started scanning and the target host is up (i.e., online).
The second line tells us the IP address or hostname of the scanned device.
The “Not shown” line indicates how many closed ports were not listed in the output. This can help you understand which ports are safe and don’t need to be checked further.
The next lines show the open ports along with their respective port numbers (e.g., 22/tcp) and services running on them (e.g., ssh, http).

Closing Open Ports

Once you know which ports are open on your Raspberry Pi, it’s time to close them if they are not in use or unnecessary. This will help protect your device from unauthorized access and improve its security. You can use the ufw (Uncomplicated Firewall) tool to manage firewall rules on your Raspberry Pi.

First, install ufw if you haven’t already:

sudo apt-get install ufw

Then, deny incoming traffic to a specific port with the following command:

sudo ufw deny <port number>

For example, to close port 80 (HTTP):

sudo ufw deny 80

To verify that the rule has been added, run:

sudo ufw status

You should see a line like this in the output:

80                         DENY       Anywhere

Now your Raspberry Pi is one step closer to being more secure. Remember to always keep your software up-to-date and use strong passwords to protect against potential attacks.

Conclusion Checking open ports on your Raspberry Pi using nmap is an essential first step towards understanding the security of your device. By closing unnecessary or unused ports, you can minimize the risk of unauthorized access and protect your data from prying eyes. Keep in mind that even closed ports are not 100% secure, so it’s important to stay vigilant and regularly update your software and patch any vulnerabilities.