2. The Context of Cybersecurity: Cyberspace 25 the Linux kernel (the core low-level OS component) with software, tools, and user interfaces called distributions (distros). The two main distributions are Debian and Ubuntu. Both of these distros are widely used among cybersecurity professionals and enthusiasts, and navigating them is not that much different from using Windows and macOS. Probably the most well-known hacker OS is called Kali Linux. As the Kali website states, “Kali Linux is an open-source, Debian-based Linux distribution geared towards various information security tasks, such as Penetration Testing, Security Research, Computer Forensics and Reverse Engineering.”5 All computers that humans interface with run an OS, and this certainly includes smartphones. The two main smartphone OSs (i.e., mobile operating systems) are Google’s Android (first released in 2008) and Apple’s iOS (first released in 2007). Android is based on Linux, but the Android OS that runs on most smartphones is Google’s proprietary version. When a computer is powered on, the operating system is the first program loaded from storage into memory. This is called booting because the computer has to lift itself up by its own bootstraps in order to get going! The OS runs continuously while the computer is on and presents a user interface so that people can interact with the computer. There are two main types of operating system user interfaces: the command-line interface (CLI), and the graphical user interface (GUI) (see Figure 2.8). CLIs are purely text-based and enable users to type in commands and read typed output. GUIs have graphics such as buttons, icons, and text fields that allow the user to point and click as well as type. GUIs are more popular with everyday users because they are intuitive to use, but CLIs are more efficient for adept users. Figure 2.8 Windows OS CLI (left) and GUI (right) for browsing files. When a program is executed on a computer, the OS loads it from storage into memory where the CPU can access its machine instructions. At this point, the program becomes a process. A process is a running program. Computers typically have many processes 5 kali.org website. The most advanced Penetration Testing Distribution. Retrieved June 2025.
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