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| Ethical Hacking |
🛡️ Ethical Hacking — Day 3
Linux, Windows & macOS Fundamentals for Ethical Hackers
⚠️ LEARNING PURPOSE ONLY: This tutorial is strictly for educational and defensive cybersecurity learning. Perform practical exercises only on computers, virtual machines, applications, networks, or labs that you own or have explicit permission to test. Never use these commands to access or disrupt unauthorized systems.
Welcome to Day 3 of the Ethical Hacking Learning Series.
On Day 2, we learned how devices communicate through IP addresses, ports, DNS, TCP/UDP, and gateways. Today, we'll learn how to work with the three major operating-system environments you'll encounter in cybersecurity: Linux, Windows, and macOS.
🎯 Day 3 Learning Objectives
Today you'll learn:
Operating-system fundamentals
Files and directories
Users and groups
File permissions
Processes
Services
Environment variables
Command-line navigation
System information commands
Basic security-oriented commands
Equivalent commands across Linux, Windows, and macOS
By the end of today, you should be comfortable opening a terminal and investigating your own computer.
1. Why Operating Systems Matter in Ethical Hacking
An ethical hacker needs to understand how operating systems work because vulnerabilities often depend on:
Users
Permissions
Processes
Services
Files
Network connections
Installed software
System configurations
For example:
Application
↓
Operating System
↓
Kernel
↓
Hardware
Understanding this structure helps you understand where security problems can occur.
2. Linux vs Windows vs macOS
| Feature | Linux | Windows | macOS |
|---|---|---|---|
| Command line | Terminal | CMD / PowerShell | Terminal |
| Common shell | Bash/Zsh | PowerShell | Zsh |
| Filesystem root | / | C:\ | / |
| User management | Users/Groups | Users/Groups | Users/Groups |
| Process tools | ps, top | Get-Process, tasklist | ps, top |
| Network tools | ip, ss | ipconfig, netstat | ifconfig, netstat |
| Package ecosystem | apt/dnf/pacman etc. | winget | Homebrew commonly used |
The commands differ, but the concepts are very similar.
3. Understanding the File System
A file system organizes information on your computer.
Linux/macOS
The filesystem begins at:
/
Example:
/
├── home
├── etc
├── var
├── tmp
└── usr
Windows
Windows commonly uses drive letters:
C:\
├── Users
├── Windows
├── Program Files
└── ProgramData
The important security concept is:
Where a file is located and who can access it matters.
🐧 Linux Practical
Open your Terminal.
Step 1 — Find your current directory
pwd
Example:
/home/user
pwd means Print Working Directory.
Step 2 — List files
ls
For detailed information:
ls -la
You may see:
drwxr-xr-x
-rw-r--r--
We'll learn exactly what these permissions mean shortly.
Step 3 — Move between directories
cd /tmp
Then:
pwd
Return to your home directory:
cd ~
Go one level up:
cd ..
Step 4 — Create a practice directory
mkdir ethical-hacking-day3
Enter it:
cd ethical-hacking-day3
Create a file:
touch notes.txt
Check it:
ls -l
🪟 Windows Practical
Open PowerShell.
Step 1 — Find your current directory
Get-Location
Short form:
pwd
Step 2 — List files
Get-ChildItem
Short form:
ls
Step 3 — Change directory
Set-Location $env:TEMP
or:
cd $env:TEMP
Step 4 — Create a practice directory
New-Item -ItemType Directory ethical-hacking-day3
Enter it:
cd ethical-hacking-day3
Create a file:
New-Item notes.txt
Check it:
Get-ChildItem
🍎 macOS Practical
Open Terminal.
Step 1 — Current directory
pwd
Step 2 — List files
ls -la
Step 3 — Navigate
cd /tmp
Then:
pwd
Return home:
cd ~
Step 4 — Create a practice directory
mkdir ethical-hacking-day3
Enter it:
cd ethical-hacking-day3
Create a file:
touch notes.txt
Check:
ls -l
🔐 4. Understanding Users
Operating systems use user accounts to control access.
A computer may have:
Administrator / Root
│
├── User A
├── User B
└── Service Accounts
An important security principle is:
Principle of Least Privilege
Users and applications should have only the permissions they actually need.
For example, a normal application generally shouldn't require unrestricted administrator/root privileges.
🐧 Linux: Who Am I?
Run:
whoami
Find user and group information:
id
You may see:
uid=1000(user) gid=1000(user)
🪟 Windows: Who Am I?
PowerShell:
whoami
You can also inspect your current user:
$env:USERNAME
🍎 macOS: Who Am I?
Terminal:
whoami
And:
id
🔐 5. File Permissions
File permissions are extremely important in cybersecurity.
Linux/macOS commonly use:
r = read
w = write
x = execute
Example:
-rwxr-xr--
Conceptually:
Owner Group Others
rwx r-x r--
This means:
Owner → read/write/execute
Group → read/execute
Others → read
Understanding permissions will become especially important when we study Linux privilege escalation later.
🐧 Linux Permission Practical
Inside your Day 3 directory:
ls -l notes.txt
Change permissions on your practice file:
chmod 600 notes.txt
Check again:
ls -l notes.txt
The file should now be accessible only to your user under the normal Unix permission model.
Restore a more common permission example
chmod 644 notes.txt
Check:
ls -l notes.txt
⚠️ Only modify permissions on files you own or are authorized to administer.
🍎 macOS Permission Practical
macOS also uses Unix-style permissions.
Run:
ls -l notes.txt
Then:
chmod 600 notes.txt
Check:
ls -l notes.txt
Restore:
chmod 644 notes.txt
🪟 Windows Permissions
Windows uses a different permissions model based heavily on NTFS Access Control Lists (ACLs).
View permissions for your practice file/directory:
Get-Acl .\notes.txt
You can also inspect the directory:
Get-Acl .
Don't modify permissions yet. Today we're learning to observe and understand them.
⚙️ 6. Processes
A process is a running instance of a program.
For example:
Browser
↓
Process
↓
Operating System
↓
CPU / Memory
Security professionals need to understand processes because malicious software, vulnerable applications, and legitimate services all run as processes.
🐧 Linux Processes
Run:
ps
For a broader view:
ps aux
You can also use:
top
Exit top with:
q
🪟 Windows Processes
PowerShell:
Get-Process
Find a specific process:
Get-Process | Where-Object {$_.ProcessName -like "*chrome*"}
You can also use:
tasklist
🍎 macOS Processes
Terminal:
ps aux
Interactive process view:
top
Exit with:
q
🛠️ 7. Services
A service is a background program that performs a specific function.
Examples:
Web server
Database server
SSH server
Print service
Update service
Services are important to security because an unnecessary or vulnerable service can increase the attack surface.
🐧 Linux Services
On many systemd-based distributions:
systemctl --type=service --state=running
You can inspect a specific service if you know its name:
systemctl status <service-name>
Don't stop or modify services during this exercise.
🪟 Windows Services
PowerShell:
Get-Service
To see running services:
Get-Service | Where-Object {$_.Status -eq "Running"}
🍎 macOS Services
macOS service management differs from Linux.
You can inspect running processes:
ps aux
You can also inspect launch services with:
launchctl list
Today we're only observing the configuration.
🌎 8. Environment Variables
Environment variables store configuration information used by applications and the operating system.
Examples include:
PATH
HOME
USER
TEMP
They are particularly important when working with:
Programming
Shell scripts
Application configuration
Development environments
Security testing
🐧 Linux
echo $PATH
View all environment variables:
env
🪟 Windows PowerShell
$env:Path
View environment variables:
Get-ChildItem Env:
🍎 macOS
echo $PATH
And:
env
🧪 Day 3 Cross-Platform Practical Lab
Create a directory called:
ethical-hacking-day3
Inside it, create:
system-info.txt
Then collect basic information about your own machine.
Linux
uname -a
whoami
pwd
ip addr
ps
Windows PowerShell
Get-ComputerInfo | Select-Object WindowsProductName, WindowsVersion
whoami
Get-Location
ipconfig
Get-Process
macOS
sw_vers
whoami
pwd
ifconfig
ps aux
The purpose is to learn how to inspect your own operating system.
🔍 Day 3 Security Mindset
When looking at a system, start asking:
Users
Who has access?
Files
Who can read or modify this?
Processes
What is currently running?
Services
What network-facing or background services exist?
Permissions
Does this application have more privileges than necessary?
Configuration
Are important settings exposed or misconfigured?
These questions form the foundation of security assessment.
📝 Day 3 Assignment
Answer these questions:
1.
What is the difference between a process and a service?
2.
What does the principle of least privilege mean?
3.
What do r, w, and x represent in Unix permissions?
4.
What command displays your current username on Linux, Windows, and macOS?
5.
What command can you use to view running processes on each operating system?
6.
What is an environment variable?
7.
Why are file permissions important for cybersecurity?
8.
What is the difference between Linux/macOS permissions and Windows ACLs?
🧪 Day 3 Challenge
On your own computer, find:
✅ Current username
✅ Operating system version
✅ Current working directory
✅ Network interface
✅ At least 5 running processes
✅ At least 3 running services
✅ PATH environment variable
Then write down what each item means.
Do not publish your complete system information, usernames, IP addresses, process lists, or other potentially sensitive information online.
⚠️ Ethical Hacking Reminder
LEARNING PURPOSE ONLY: Today's commands are intended for learning and authorized system administration/security practice. Use them only on systems you own or are explicitly authorized to administer or test. Never use administrative commands, permission changes, process manipulation, or service controls against unauthorized systems.
✅ Day 3 Summary
Today you learned:
Operating-system fundamentals
Linux filesystem
Windows filesystem
macOS filesystem
Users and groups
File permissions
Windows ACLs
Processes
Services
Environment variables
Basic system investigation
Equivalent commands across Linux, Windows, and macOS
The goal isn't to memorize hundreds of commands.
Understand what the command is doing, why you're running it, and what the result tells you.
🔜 Day 4 — Command Line & Shell Fundamentals
Tomorrow we'll go deeper into:
🐧 Linux: Bash commands and shell navigation
🪟 Windows: PowerShell fundamentals
🍎 macOS: Zsh/Terminal fundamentals
We'll cover:
cd,ls,pwdFiles and directories
Searching for files
Viewing file contents
Pipes
|Redirection
>,>>Command chaining
Searching command output
Basic shell scripting
Practical exercises on all three operating systems
🔐 Learn → Practice → Understand → Secure.
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