CyberSecurity & DevSecOps Expert: Develop, PenTest, and Deploy Secure Applications

When a computer receives data over a network, it faces an immediate challenge: multiple applications are running simultaneously — a browser, an email client, a file transfer tool — and all of them may be receiving data at the same time. How does the ...

**Theoretical Recap** The TCP (Transmission Control Protocol) three-way handshake is the foundational mechanism by which two hosts establish a reliable connection before any data exchange occurs. It operates at Layer 4 (Transport) of the OSI model an...

Now that you have explored the first three layers of the OSI model — Physical, Data Link, and Network — you have seen how data travels as electrical signals, how Ethernet frames are built, and how routers forward packets across networks using IP addr...

## Project Overview In this mini-project, you will consolidate everything you have learned about OSI layers 1 through 3 by tracing, capturing, and documenting the complete journey of a network packet from your machine to a public website. This is not...

THEORETICAL RECAP Traceroute is a network diagnostic tool that maps the path packets take from your machine to a destination host, revealing each intermediate router (hop) along the way. It works by sending packets with incrementally increasing TTL (...

THEORETICAL RECAP Traceroute (or tracert on Windows) is a network diagnostic tool that maps the path packets take from your machine to a destination host, revealing each intermediate router — called a 'hop' — along the way. It operates at Layer 3 (Ne...

INTRODUCTION AND POSITIONING IN THE OSI MODEL You have already explored Layers 1 and 2 of the OSI model. You know that Layer 1 (Physical) handles signals and transmission media, and that Layer 2 (Data Link) manages the framing of data, error detectio...

THEORETICAL RECAP An Ethernet frame is a structured unit of data that operates at Layer 2 (Data Link) of the OSI model. It carries a payload from one MAC address to another within the same network segment. A standard Ethernet frame contains the follo...

THEORETICAL RECAP An Ethernet frame is the fundamental unit of data at Layer 2 (Data Link) of the OSI model. When two devices communicate on a local network, data is broken down into frames before being transmitted over the physical medium. Each Ethe...

Now that you have explored Layer 1, which deals with physical signals, cables, and transmission media, it is time to move up one level in the OSI model. Layer 2, called the Data Link layer, sits directly above the physical layer and adds the first la...

THEORETICAL RECAP At OSI Layer 1 (Physical), the cable is not just a wire — it is a medium that determines speed, distance, interference resistance, and ultimately, the reliability of your entire network stack. Three main cable families dominate ente...

You have already explored what the OSI model is, how encapsulation works, and what IP addresses and packets look like in practice. You even observed real network traffic with tools like ping and Wireshark. Now it is time to go deeper into the foundat...

**Theoretical Recap** The OSI model (Open Systems Interconnection) is a conceptual framework that standardizes network communication into 7 distinct layers: Physical (1), Data Link (2), Network (3), Transport (4), Session (5), Presentation (6), and A...

In the previous activities, you explored the basic vocabulary of networks, learned to identify IP addresses, observed packets with the ping command, and distinguished between switches and routers. You now have a solid mental picture of what a network...

**Theoretical Recap** Before diving into the simulator, let's consolidate what you've covered so far. A network is a set of interconnected devices (hosts) that exchange data through links in the form of packets. Each packet carries a source and desti...

Before diving into the differences between a switch and a router, it is essential to understand what a network topology is and why it matters for anyone working in cybersecurity or DevSecOps. A network topology describes the physical or logical arran...

**Theoretical Recap** An IP address (Internet Protocol address) is a unique numerical identifier assigned to every device connected to a network. IPv4 addresses are written in dotted-decimal notation (e.g., 192.168.1.1), composed of four octets rangi...

**Theoretical Recap** ICMP (Internet Control Message Protocol) is a network-layer protocol (OSI Layer 3) used primarily for diagnostic and error-reporting purposes. Unlike TCP or UDP, ICMP does not carry application data — it carries control messages...

Now that you are familiar with the basic vocabulary of networks — hosts, links, and packets — it is time to go deeper into two fundamental concepts that underpin virtually every communication on the internet and on private networks: the Internet Prot...

**Theoretical Recap** Before diving into the workshop, let's consolidate the core concepts you've encountered so far. A network is made up of hosts (any device with an IP address: computer, smartphone, printer, router, smart TV), links (the physical ...

Understanding how networks work is the foundation of cybersecurity. Before diving into attack techniques, penetration testing tools, or secure deployment pipelines, you need to be fluent in the basic vocabulary that describes what a network is and ho...

Welcome to the chapter on Fundamentals of OSI Networks, Protocols, and Models. This chapter is your essential starting point before diving into any cybersecurity or DevSecOps practice. Whether you are aiming to conduct penetration tests, identify vul...

Congratulations on reaching the end of the introductory chapter of this course. Before moving forward, it is essential to consolidate everything you have learned so far and to understand how it connects to what lies ahead. This summary is not simply ...

THEORETICAL RECAP A vulnerability report is the primary deliverable of any security assessment. It transforms technical findings into actionable intelligence for developers, managers, and security teams. A well-structured report answers four essentia...

**Theoretical Recap** A vulnerability report is a structured document that communicates security findings to both technical and non-technical stakeholders. Understanding how to read and extract key information from such a report is a foundational ski...