Essential Security Tools: Kali Linux

Analysts and security professionals must always possess robust toolkits to combat rapidly advancing threats in our ever-evolving cyberspace. These toolkits must contain certain essentials, and to remain relevant as security professionals, we must adopt new tools. This series will explore some critical tools and their relevance within cybersecurity.

First on the list is Kali Linux, a powerful, open-source operating system specially built for cybersecurity. From penetration testing to ethical hacking, digital forensics, threat hunting, and advanced incident response, Kali has capabilities that will continue to wow enthusiasts and seasoned professionals alike.

Some key benefits of using Kali include.

• Kali is highly customizable, allowing users to add or remove tools based on the peculiarities of their use case.
• Kali comes with over 600 unique tools for security analysis tasks (e.g., network scanning, malware analysis, and more.), making it indispensable.
• Kali is flexible and can run as a portable from a USB without installation, making it a versatile option for users.
• Kali boasts of a robust community base and extensive documentation to support users.

Installing Kali Linux.

To install Kali Linux, I strongly recommend getting the software from the official Kali.org website. This article will not cover the installation process; here are some walkthrough videos on installing the OS.

I will only discuss my experience during the installation and share some insights from what I learned.

The official Kali website offers several installer options, such as ISO images, prebuilt virtual machine (VM), and Windows subsystem layer (WSL) versions. It even sports a mobile (Android) version. I explored the VM and ISO versions, which were the same, with a few variations in the installation workflow.

I always recommend using a hypervisor. VirtualBox, VMWare Workstation, VMWare Fusion (for Macs), and Windows Hyper-V are all great options. I currently use VMWare Workstation.

Installation using the VM builds takes a few minutes, while the ISO installations are pretty detailed and can take fifteen minutes to an hour to complete.

Here is where my inquisitive mind got the best of me, and I learned a valuable lesson. After successfully installing the OS, I updated the installed packages using the command (as recommended).

sudo apt-get update        

I decided to take it further and upgrade the OS using the command.

sudo apt upgrade        

PS: If you're unwilling to break stuff and fix it back, I would not recommend taking this step.

After about forty-five minutes to an hour, I completed the upgrade, and the machine rebooted with a black screen.

It turns out that Kali Linux's default desktop display manager is 'lightdm', which has been known to fail due to compatibility issues with specific display drivers (e.g., NVIDIA). I currently run an Intel Iris Plus Graphics card on my machine; however, I still ran into the 'black screen' problem.

The most popular solution to this issue involves rebooting the machine and booting into it using any TTY terminal. Unfortunately, that did not work for me, as my TTY terminals kept disconnecting after a few seconds.

Lesson #1:

After a successful OS installation, I recommend taking a snapshot and saving it as a baseline version. This single action helped me recover my OS installation faster than a fresh installation.

Lesson #2:

There are multiple ways to solve a problem. Never be content knowing only one path to the solution.

Unable to use the TTY terminal, I resorted to rolling back the upgrade installation (using the baseline snapshot I had earlier created) to find an alternate logical method to fix the problem.

Using the baseline snapshot (which had the 'lightdm' working), I switched the display manager to a different one using the command.

sudo dpkg-reconfigure lightdm        

Let me pause here: Kali Linux has three major desktop display manager options.

• Gnome DM: Prominently known for its sleek design and ease of use, it is most suitable for users who want a polished login and user interface. The most recent version is GDM3.
• Light DM: A lightweight display manager preferred for speed and flexibility with multiple desktop environments.
• Simple Desktop DM:??Also referred to as 'SDDM,' this display manager is preferred for its attractiveness and compatibility with other environments.

Once I switched to SDDM, I attempted the upgrade again and completed it without a glitch. I rebooted the machine with my fingers crossed and was delighted to see the login screen.

Lesson #3:

Be obsessed with progress, no matter the hurdles you face and how slow you progress. Direction is more important than speed!

Not one to back down easily, I decided to test my final hypothesis. If 'lightdm' works perfectly before the upgrade, after upgrading using 'sddm,' I should be able to switch back to 'lightdm' without the black screen. I made the final switch back to 'lightdm' using the command.

sudo dpkg-reconfigure lightdm        

Here are screenshots of the final result.

To learn more about Kali Linux, here are some additional resources:

1. OffSec KLCP Course - https://www.offsec.com/courses/pen-103/
2. Empirical Training (Free Tier) - ??Cyber Swiss Army Knife
3. Empirical Training (Gold Tier) - Week 2: Kali Setup
4. Kali Official Website (Tools Documentation) - https://www.kali.org/tools/
5. FreeCodeCamp (on YouTube) - Linux for Ethical Hackers (Kali Linux Tutorial)