Weekend Project: Part 1 – Securing a Raspberry Pi

Recently I dug out the old Raspberry Pi with the aim of using it as a VPN and a DNS backhole. I have always hand a handle on my privacy online but since looking up a new office chair online last week Facebook has provided me with an onslaught of ads for various office chairs, normally I brush this off tracking cookies never really bother me to much but, for some reason this got me triggered. So this weekend I will be turning my Raspberry Pi into a VPN and DNS black hole. The Raspberry Pi will sit on my home network, any devices phone’s, laptops, PC’s etc can be configured to send traffic through the Pi and then out to the internet fully encrpted.

First things first is down download the latest version of Raspbian, you can find it here : https://www.raspberrypi.org/downloads/raspbian/

I am pretty well versed in a Linux/Unix command line and am comfertable in my Linux knowlage to know the various tools, where they are and if they are not present where to get them so, I went for the Raspian Lite image just to keep things as lean as possible.

Tip: If you plan to run your Pi as a headless server, after writing the Raspbian image to an SD Card create a file called ‘ssh’ (file can be empty) on the card to enable ssh on first boot. This used to be enabled by default but a recent change due to worries of attackers high jacking un-secure Raspberry Pi’s prompted the folks over an Pi HQ to turn SSH as default. This tip saves you having to connect a monitor, keyboard & mouse to your Pi just to turn on SSH.

First Things First

At this point I assume you have your Raspberry Pi powered on, to find you Pi’s IP address you can look up your router to see whats connected or try to ping raspberrypi.local. Once you have the IP you can ssh using Putty or Terminal with the following command;

ssh -l pi

Defualt password for pi user is raspberry

Change pi users password

At the end of this guide we will delete the pi user from the system but first things first lets change that default password. Just type the below;

pi@raspberrypi:~ $ passwd
Changing password for pi.
Current password:
New password:
Retype new password:
passwd: password updated successfully

Now that the password has been changed we will update the Pi so we are running the latest and greatest. The example below shows the command to run, although my Pi is already updated so it shows as no updates, expect this to take 10-15min download and install updates on your Pi.

pi@raspberrypi:~ $ sudo apt-get update && sudo apt-get upgrade -y && sudo apt-get dist-upgrade
Hit:1 http://raspbian.raspberrypi.org/raspbian buster InRelease
Hit:2 http://archive.raspberrypi.org/debian buster InRelease
Reading package lists… Done
Reading package lists… Done
Building dependency tree
Reading state information… Done
Calculating upgrade… Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
Reading package lists… Done
Building dependency tree
Reading state information… Done
Calculating upgrade… Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.

Now we have an up-to-date system lets create a new user and remove the default pi user. A new user can be created with the useradd comand. We will set a password for the new user.

pi@raspberrypi:~ $ sudo useradd paz
pi@raspberrypi:~ $ sudo usermod -a -G adm,dialout,cdrom,sudo,audio,video,plugdev,games,users,input,netdev,gpio,i2c,spi paz

pi@raspberrypi:~ $ sudo passwd paz
New password:
Retype new password:
passwd: password updated successfully
pi@raspberrypi:~ $
pi@raspberrypi:~ $ exit
Connection to closed.

Lets disconnect as the pi user and connect as our new user, in my case ‘paz’.
pazy@Andrews-Air Downloads % ssh -l paz
paz@'s password:
Linux raspberrypi 4.19.75-v7+ #1270 SMP Tue Sep 24 18:45:11 BST 2019 armv7l

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
paz@raspberrypi:~ $

Finally we can delete the pi user from our Raspberry Pi;

paz@raspberrypi:~ $ sudo deluser pi
Removing user pi' ... Warning: grouppi' has no more members.

paz@raspberrypi:~ $ sudo rm -rf /home/pi

We now have an up-to-date Pi and new user different to the default to connect with. To many this is enough but if your intent to connect your Pi to face the internet then you should be performing further steps to prevent attacks. On th next section we will guide you though this.

The Next Level

To secure your Raspberry Pi further we will insall fail2ban and change the defauly SSH port from 22 to something of your choosing.

Changing SSH port is simple just edit the file /etc/ssh/ssd_config, where you see the entry #Port remove the # and change the port number from the default 22 to something of your choosing. In my case I use 2222.

Once you update /etc/ssh/ssd_config you will need to restart the ssh service using the below command;

paz@raspberrypi:~ $ sudo service ssh restart

If we exit our session on our Pi and try and re-connect you will see our connection fails as we no longer have ssh running on port 22, we must use -p option to specify port at 2222.

pazy@Andrews-Air Downloads % ssh -l paz -p 22
ssh: connect to host port 22: Connection refused
pazy@Andrews-Air Downloads %
pazy@Andrews-Air Downloads %
pazy@Andrews-Air Downloads % ssh -l paz -p 2222

Next we will install fail2ban. fail2ban analyses system logs for failed attempts to login to you Pi, should X number of attempts result in a fail that IP address is then banned from accessing the host. This provided pretty good protection from anyone trying to brute force thier way onto your Pi.

To install fail2ban do the following;

paz@raspberrypi:~ $ sudo apt-get install fail2ban

With fail2ban you much copy the .config file to .local as per below;

paz@raspberrypi:~ $ sudo cp /etc/fail2ban/jail.conf /etc/fail2ban/jail.local

If you wish to edit configuration for example the number of bad attempts allowed before a ban edit the jail.local file.

While the article does seem pretty long it will only take 15min or so to run through the commands. Next I will write about setting up a VPN and Pi-hole on your Pi.

2 thoughts on “Weekend Project: Part 1 – Securing a Raspberry Pi

    1. It working well of 16k queries across 11 devices 20% has been blocked as some form of tracker, Youtube and Instagram are so far the biggest offenders at trying to tack what we are looking at.

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