Introduction to Linux for Security Professionals

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🐧 Introduction to Linux for Security Professionals

🔹 Why Linux for Security?

Linux is the most important OS for cyber security because:

✔ Open Source
✔ Highly secure
✔ Powerful command line
✔ Used on servers
✔ Best for penetration testing
✔ Customizable

Most security tools are built for Linux.

🔹 Popular Linux Distros for Security

  • Kali Linux – Penetration testing

  • Parrot OS – Security + privacy

  • Ubuntu – General + servers

  • RedHat – Enterprise security

👉 Kali Linux is most popular for hackers and security professionals.

🔹 Linux Architecture (Simple)

User → Shell → Kernel → Hardware

  • Shell – Command interpreter

  • Kernel – Core of OS

  • File System – Stores data

🔹 Linux File System Structure

DirectoryUse
/Root
/homeUser files
/etcConfig files
/binCommands
/varLogs
/tmpTemporary files
/usrPrograms

🔹 Basic Linux Commands (Security Must-Know)

📁 File Commands

ls        # list files
cd        # change directory
pwd       # current path
mkdir     # create folder
rm        # delete
cp        # copy
mv        # move

👤 User Commands

whoami
id
passwd
adduser

🌐 Network Commands

ifconfig / ip a
ping
netstat -tulnp
ss -tulnp
nmap

🔐 Permission Commands

chmod
chown
ls -l

Example:

chmod 755 file.sh

📄 Process Commands

ps
top
kill

🔹 Linux Permissions (Security Core)

Format:

-rwxr-xr--

  • r = read

  • w = write

  • x = execute

Owner | Group | Others

🔹 Package Management

Install tools:

apt update
apt install nmap

🔹 Logs (For Security)

Important logs:

/var/log/auth.log
/var/log/syslog

Used for detecting attacks.

🔹 Security Tools in Linux

  • nmap – scanning

  • tcpdump – packet capture

  • wireshark – analysis

  • metasploit – exploitation

  • hydra – brute force

  • netcat – networking

(Use only legally.)

🔹 Why CLI is Important for Security

✔ Faster
✔ Automation
✔ Remote access
✔ Powerful scripting

🔹 Best Practices for Security Pros

✔ Use non-root user
✔ Update system
✔ Use firewall (ufw)
✔ Monitor logs
✔ Strong permissions
✔ SSH security

📝 Exam Short Notes

  • Linux is open source OS.

  • Kali is security distro.

  • chmod controls permissions.

  • /etc stores config files.

  • CLI is powerful for security.

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