Raspberry Pi is a common requirement for security professionals to gather information from remote sites in large distributed organizations. Many people leverage commercial tools that specialize in vulnerability assessments for this situation; however, you may not have access to such tools due to a limited budget or vendor partnership requirements. An example of this situation is when the authors of this book had to take part in a security assessment that included multiple locations all over the world. For this project, it was not feasible to travel to every location to deliver local penetration testing services. To overcome this, we sent Raspberry Pi devices configured with Kali Linux to each location and remotely assessed the network for vulnerabilities at a very affordable price. We will cover this engagement example in more detail at the end of this chapter.

Another valuable use case for a Raspberry Pi is when a security professional wants to leave a device on-site...

As we have stated in other chapters, the Raspberry Pi is not a powerful machine. To overcome this weakness, it is best practice to capture data in a controlled manner or leverage offline computing when using Kali Linux on a Raspberry Pi. We found that not doing so would either overwhelm the processors when using most of the attack tools or quickly consume the limited local storage space when viewing captured data. We will cover filtering captured data in Chapter 3, Penetration Testing, under the Tuning your network capture section.

When planning to remotely access multiple Raspberry Pi systems, we recommend setting up a central Command and Control (C&C) server rather than accessing each box individually. The C&C server should be a more powerful system such as a traditional server so it can focus on CPU intensive tasks such as breaking passwords through brute force. More importantly, tasks can also include using the C&C server to perform the actual...

The Kali Linux ARM image we covered in Chapter 1, Raspberry Pi and Kali Linux Basics, has already been optimized for a Raspberry Pi. We found however that it is recommended to perform a few additional steps to ensure you are using Kali Linux in the most stable mode to avoid crashing the Raspberry Pi. The steps are as follows:

Overclocking the Raspberry Pi can improve the performance. The risk of doing this can also greatly reduce the life of the hardware. Overclocking may require more power from the Raspberry Pi, so if you are powering it from a weak power source, overclocking could cause issues. We have had some problems resulting in what appears to be corruption in microSD cards and operating systems when overclocking the Raspberry Pi.

To overclock the Raspberry Pi, you can use the raspi-config application for advanced hardware manipulation. Unfortunately, this application does not come with the Kali Linux image and requires some configuration. Don't worry; we have made the following steps pretty easy for you to follow. They are:

When you purchase a Wi-Fi adapter for your Raspberry Pi, you want to make sure it not only works with the Raspberry Pi, but also works with Kali Linux. Luckily, almost every Wi-Fi adapter we used works with both the Raspberry Pi and Kali Linux. In this book, we are using the CanaKit Wi-Fi dongle, as shown in the following image:

CanaKit makes an extremely popular Raspberry Pi kit that ships with this version of the Wi-Fi adapter. You can also purchase an adapter separately. If you need to purchase a separate card, make sure it is one that works with Debian Linux.

Once you connect your Wi-Fi adapter, you should first verify that the system shows it is functioning properly. You can do this by issuing the iwconfig command in a terminal window as shown in the following screenshot:

You should see a wlan0 interface representing your new wireless interface. The next step is to enable the interface...

You can use 3G USB modem cards with Kali Linux and connect to your Raspberry Pi over cellular for stealthy remote access. Each card is manufactured a little differently, and therefore the setup may vary based on the type of 3G card and service provider. Our recommendation is using a MiFi (short for Mobile Wi-Fi) hotspot and connecting Kali Linux through a Wi-Fi adapter; however, if you want to use a 3G USB modem, make sure you verify it works with Debian.

In our next example, we use the Huawei 3G USB modem connect card. This is a 3G GSM card that works with most frequencies around the globe.

Here are the steps to set up this card:

The Secure Shell (SSH) gives you full access to the Kali Linux operating system on a Raspberry Pi from a remote location. It is the most common way to manage Linux systems using a command line. Since the Kali Linux GUI is not needed for most penetration testing exercises, we recommend that you use SSH or command-line utilities whenever possible. We found some installations of Kali Linux have SSH enabled while others may need you to install the OpenSSH server.

You should first verify whether the SSH service is installed. Type in the service --status-all command to check whether the SSH service is running. If you see + as shown in the following screenshot, you are good to go. If you see a - sign, then you will need to install the OpenSSH server.

To install the OpenSSH server, open a command-line terminal and type apt-get install openssh-server to install the SSH services. You will need to start the SSH services by issuing the service ssh start command as shown in the...

At this point, you have a Raspberry Pi ready for remote management using SSH. This is good; however, the keys that are installed by default are extremely predictable with every other default installation for OpenSSH. Although this is optional, best practice is changing the default keys. After all, it would be embarrassing if your penetration testing machine got hacked.

Here are the steps to create a new SSH key for your Kali Linux system: