• LAN(local area network)

A network within a small area (like a building)

• WAN(Wide area network)

Connects LANs across longer distances. 

• IP Address

A unique address for each device on a network.

• MAC Address

A hardware address used to identify devices on a LAN.

1. Physical- Cables, switches, etc

2. Data link- MAC addresses, switches.

3. Network- IP addresses, routers.

4. Transport- TCP/UDP Protocols.

5. Session- Maintains connections.

6. Presentation- Data translation/encryption.

7. Application- user interfaces. 

3. IP Addressing and subnetting 

• IPv4- e.g., 192.168.1.1

• Subnetting- Dividing a network into a smaller parts for better management and security.

4. Routing and Switching

• Switch- Connects devices in the same network.

• Router- Connects different networks.

• VLANs (Virtual LANs)- separate logical networks within a physical switch.

5. Network Protocols

•  TCP/IP- Main protocol suite used in networking.

• DNS- Converts domain names into IP Addresses.

• DHCP- Assigns IP addresses automatically.

• HTTP/HTTPS- Web communication protocols.

• FTP- Tranfers files.

6. CISCO IOS & CLI 

• Cisco devices use IOS (Internetwork Operating System)

• You’ll configure devices using CLI (Command Line Interface)

enable                   # Enter privileged mode

configure terminal       # Enter global config mode

interface FastEthernet0/1 # Enter interface config

ip address 192.168.1.1 255.255.255.0

no shutdown              # Activate the interface

7. Network Security basics

• Access Control Lists (ACLs): Control who can access network resources.

• Port Security: Limit devices on a switch port.

Kali Linux & Penetration Testing:

What is kali Linux?

Kali Linux is a specialised linux distribution built for penetration testing, ethical hacking, and digital forensics. It comes preloaded with hundreds of tools used by cybersecurity professionals. 

• Based on Debian Linux 

• Maintained by Offensive Security 

• Free and open-source.

Penetration Testing (Pen Testing) is a simulated cyberattack on a system, network, or application to find and fix security vulnerabilities before real attackers do.

Pen testers act like ethical hackers — they break in legally to help improve security.

Kali Linux tools for Pen testing

Here are a few tools grouped by category.

1. Information Gathering

• Nmap- Scans network and finds open ports.

• Whois- Info about domains.

• theHarvester- Gathers emails, subdomains, etc.

2. Vulnerability Analysis 

• Nikto- Web server vulnerability scanner.

• OpenVAS- full featured vulnerability scanner.

3. Exploitation tools

• Metasploit Framework- Exploit systems, test payloads. 

• SQLmap- Detect and exploit SQL injection flaws.

4. Wireless Attacks

• Aircrack-ng – Cracks Wi-Fi passwords.

• Reaver – Attacks WPS in routers.

5. Password Attacks

• John the Ripper- Password Cracking tool

• Hydra- Brute force login credentials.

6. Sniffing & Spoofing 

• Wireshark- Capture and analyze network packets.

• Ettercap- Man-in-the-middle attacks.

Common Pen Testing Stages (PTES Methodology)

1. Reconnaissance (Recon):

Gather info about the target (passive & active)

2. Scanning: Identify open ports and services.

3. Exploitation: Use vulnerabilities to gain access.

4. Privilege Escalation: Gain higher-level access.

5. Post Exploitation: Analyze what was accessed.

6. Reporting: Document findings and suggest fixes.

Is Pen Testing Legal?

Only if you have permission from the owner of the system. Without consent, it's considered illegal hacking.

Learning Resources 

• TryHackMe, Hack the Box- Hands-on labs.

• OWASP Top 10- Common web vulnerabilities.

• Metasploit Unleashed- learn exploitation tools.

Cyber security and ethical Hacking tools:

1. Reconnaissance(Info Gathering)

• Nmap- Network scanner for finding open ports/services.

• theHarvester- Gathers emails, domains, usernames from public resources.

• Maltego- Visual link analysis for relationships and data mapping.

• Recon-ng- Recon framework like Metasploit but for recon.

2. Scanning & Vulnerability Analysis

• Nikto- Web server scanner for outdated software and dangerous files.

• OpenVAS- Open-source vulnerability scanning.

• Nessus- Comprehensive vulnerability assessment tool.

• WhatWeb/Wappalyzer- Detects website technologies.

3. Exploitation

• Metasploit Framework- Powerful tool for exploiting vulnerabilities.

• SQLmap- Automates SQL injection detection and exploitation.

• BeEF(Browser Exploitation Framework)- Exploits vulnerabilities in web browsers.

• Aircrack-ng– Cracks Wi-Fi passwords using captured packets.

• Reaver– Attacks WPS to retrieve WPA/WPA2 passphrases.