Protocols and Servers

This room introduces several protocols commonly used across networks:

• HTTP
• FTP
• POP3
• SMTP
• IMAP

These protocols form the foundation of how you browse the web, transfer files, and send and receive email. Understanding how they work at a low level is essential for anyone pursuing a career in cybersecurity, whether in penetration testing, network defence, or security engineering.

Each protocol task is designed to show what happens beneath the surface, which is usually hidden by a GUI (Graphical User Interface). You will "talk" using the above protocols with a simple Telnet client to understand what your GUI client is doing under the hood. The purpose is not to memorise the protocol commands but rather to observe the protocol while it is working.

Why Learn These Protocols Today?

You might wonder why you are studying protocols that are decades old. There are several important reasons.

First, these protocols are still in use. While most public-facing services now use encrypted versions (HTTPS, SFTP, IMAPS), the underlying protocol mechanics remain the same. The commands you send over HTTPS are the same HTTP commands, wrapped in TLS encryption.

Second, you will encounter cleartext protocols during penetration tests and security assessments. Legacy systems, internal networks, IoT devices, and misconfigured services often still use unencrypted protocols. Recognising and exploiting these weaknesses is a core penetration testing skill.

Third, understanding the protocol helps you understand the attacks. When you know how SMTP works, you understand why email spoofing is possible. When you understand HTTP, web application vulnerabilities make more sense. This foundational knowledge makes you a better security professional.

This room also discusses some of the insecurities inherent in these protocols. In particular, the focus is on passwords sent in cleartext. When credentials are transmitted without encryption, anyone with access to the network traffic can capture them. This was acceptable when these protocols were designed for trusted academic networks, but it is a serious vulnerability on modern networks.

In the follow-up room, Protocols and Servers 2, you will explore how these protocols can be secured using TLS encryption, and examine attacks such as sniffing, man-in-the-middle, and password attacks in more detail.

Prerequisites

This room assumes a working understanding of TCP/IP, ports, and the client-server model. You should also be comfortable with the Linux terminal. If you need a refresher on any of these topics, complete the following first:

• Networking
• Linux Fundamentals