This is episode 2 of my Cybersecurity Roadmap series, where I learn cybersecurity in public. Last time: what cybersecurity is and the CIA triad. Today: the computer basics you need before any hacking or defending makes sense.

You cannot protect what you do not understand. So let us build the mental model.

1. Hardware: what actually runs your code

  • CPU — executes instructions. Every program, including malware, is ultimately instructions for the CPU.
  • RAM — fast, temporary memory. Turn the power off and it is gone. Passwords and keys sitting in RAM can be stolen while the machine runs.
  • Storage (SSD/HDD) — permanent memory. Deleted files are often recoverable, because "delete" usually just marks space as reusable.
  • Network card — connects the machine to other machines. Every attack from the internet arrives through it.

Security lesson: data in RAM is exposed while the machine runs, and "deleted" does not mean "gone".

2. Operating system: the boss of the machine

The OS (Windows, Linux, macOS) sits between programs and hardware. It decides:

  • Which program runs when (processes)
  • Who can read or change which file (permissions)
  • Which program may use the network (firewall rules)

Two security ideas live here:

  • Processes: every running program is a process. Malware is just a process you did not want. Task Manager (Windows) or ps (Linux) shows you what is running.
  • Users and permissions: files and programs have owners and permission levels. A normal user account cannot change system files; an administrator can. This is why you should not browse the web as administrator — any malware you run inherits your permissions.

3. Files, extensions, and why they matter

A file's extension hints at what it is — but it is only a hint:

  • .txt, .pdf, .jpg — usually data, not programs
  • .exe, .bat, .sh — programs that run when opened
  • .docx, .xlsx — documents that can contain macros (code!) — a classic malware carrier

Security lesson: "invoice.pdf.exe" is a program, not a PDF. Windows hides extensions by default — turn "show file extensions" on. It is a five-second change that stops a whole class of tricks.

4. The command line is not optional

A lot of security work happens in the terminal: checking processes, inspecting files, testing networks. You do not need to memorize everything — you need to be comfortable with:

  • Listing files and moving between folders (ls, cd, dir)
  • Reading a file (cat, type)
  • Seeing what is running (ps, Task Manager)
  • Checking network connections (netstat, ss)

If the command line scares you, practice ten minutes a day. It pays off in every later episode.

5. Updates: the most boring, most important defense

Most successful attacks do not use genius zero-days. They use known vulnerabilities in unpatched software — bugs the vendor already fixed. Updating your OS, browser, and apps closes those holes. Automatic updates exist for a reason: turn them on.

Quick checklist before the next episode

  • [ ] You can explain CPU, RAM, storage, and network card in one sentence each
  • [ ] You know what a process is and how to list running ones
  • [ ] You know why running as administrator is risky
  • [ ] File extensions are visible on your machine
  • [ ] Your OS and browser are up to date

Next episode: Networks — how data actually moves, and why that matters for attackers and defenders. Follow along, and tell me in the comments: Windows, Linux, or macOS — what do you learn on?