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

Variables and data types are the absolute foundation of any Python program. Before writing any security automation script — whether to scan a network, parse HTTP responses, or manipulate file contents — you must understand how Python stores, names, a...

When working with Python, especially in a cybersecurity or automation context, one of the first professional habits to adopt is the use of virtual environments. This chapter explains what a virtual environment is, why it is essential, and how to crea...

Before writing a single line of Python code for security automation, you need a properly configured work environment. This chapter covers the essential steps: installing Python, choosing and setting up a code editor, creating isolated project environ...

Welcome to the chapter on Python programming basics for security automation. This chapter is designed specifically for beginners who are entering the field of cybersecurity and DevSecOps, and who want to use Python as a practical tool to automate sec...

This concluding chapter serves as a structured review of everything covered throughout the 'Fundamentals of OSI networks, protocols and models' section. It is designed to consolidate your understanding, identify any remaining gaps, and confirm that y...

At this stage of the course, you have covered a rich and dense set of topics: from the Open Systems Interconnection model and its seven layers, to the Address Resolution Protocol and the Dynamic Host Configuration Protocol, the Network Address Transl...

## Project Overview This mini-project is the capstone activity for the 'Fundamentals of OSI Networks, Protocols and Models' chapter. You will produce a fully annotated diagram tracing the complete lifecycle of an HTTP request — from the moment a user...

**Theoretical Recap** HTTP (HyperText Transfer Protocol) operates at Layer 7 (Application) of the OSI model, sitting on top of TCP (Layer 4), IP (Layer 3), and ultimately Ethernet (Layer 2). When a browser sends an HTTP request, it first establishes ...

In the previous activities, you explored the lower layers of the OSI model: the physical layer, the data link layer, the network layer (with IP addressing, routing tables, and subnetting), and you practiced with Network Address Translation and Domain...

**Theoretical Recap** The hosts file is one of the oldest name resolution mechanisms in computing, predating DNS entirely. Located at `/etc/hosts` on Linux/macOS and `C:\Windows\System32\drivers\etc\hosts` on Windows, it acts as a local, static looku...

**Theoretical Recap** DNS (Domain Name System) is the internet's phone book: it translates human-readable hostnames (e.g., example.com) into IP addresses that routers and hosts can use. A DNS lookup follows a strict hierarchical resolution chain: you...

DNS, which stands for Domain Name System, is one of the most fundamental protocols of the modern internet. Without it, users would need to memorize the numerical IP addresses of every website or service they want to reach. Instead, DNS allows the use...

**Theoretical Recap** Network Address Translation (NAT) is a mechanism that rewrites IP headers at the boundary between a private network and the public internet. When a packet leaves your LAN, the router replaces the source private IP (e.g., 192.168...

Network Address Translation, commonly abbreviated as NAT, is a mechanism that allows one or more private IP addresses to be mapped to one or more public IP addresses. It operates at the boundary between a private network (such as a home or corporate ...

Understanding how network connections are tracked and how firewalls make decisions about traffic is a foundational skill for any cybersecurity professional. In the previous activities, you explored how TCP handshakes work, how to capture and filter t...

**Theoretical Recap** A routing table is a data structure stored in the kernel of an operating system that determines how network packets are forwarded from one network interface to another. Every Linux machine — whether a workstation, server, or vir...

Routing is one of the most fundamental mechanisms in computer networking. It is the process by which data packets travel from one network to another until they reach their destination. Understanding how routing works is essential for anyone entering ...

**Theoretical Recap** A subnet (subnetwork) is a logical subdivision of an IP network. The core tool for defining subnets is CIDR (Classless Inter-Domain Routing) notation, written as an IP address followed by a prefix length (e.g., 192.168.1.0/24). ...

**Theoretical Recap** An IP address in IPv4 is a 32-bit number divided into two parts: the network portion and the host portion. CIDR notation (Classless Inter-Domain Routing) expresses this split using a suffix like /24 or /26, which indicates how m...

Understanding how IP addresses are organized and divided is a fundamental skill for anyone working in cybersecurity or network administration. You have already explored ports, transport protocols, and packet capture with tools like Wireshark and Nmap...

**Theoretical Recap** DNS (Domain Name System) is the protocol responsible for translating human-readable domain names (e.g., google.com) into IP addresses that machines can route. By default, DNS operates over UDP on port 53 — a deliberate design ch...

When you open Wireshark and start a capture on a busy network interface, you are immediately flooded with hundreds or even thousands of packets per second. Without a way to narrow down what you see, finding the traffic you care about becomes nearly i...

**Theoretical Recap** The TCP three-way handshake is the mechanism by which two hosts establish a reliable connection before any data is exchanged. It consists of three segments: SYN (client initiates, proposes an Initial Sequence Number), SYN-ACK (s...

Wireshark is one of the most widely used network protocol analyzers in the world. It allows you to capture and interactively browse the traffic running on a computer network. In the context of cybersecurity and DevSecOps, Wireshark is an essential to...

**Theoretical Recap** A port is a logical endpoint at the transport layer (Layer 4) that allows a host to run multiple network services simultaneously — this is the multiplexing concept you studied in the previous lesson. When you connect to a web se...