CyberCode Academy

Course 17 - Computer Network Security Protocols And Techniques | Episode 1: Computer Network Security: Foundations, Core Aspects

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In this lesson, you’ll learn about:
  • The fundamental goals of computer network security
  • The four core security properties used to protect network communications
  • The classic security model involving Alice, Bob, and Eve
  • Common threat behaviors observed in insecure communication channels
Introduction This lesson introduces the foundations of computer network security by explaining its core objectives and the main actors involved in secure and insecure communications. To simplify complex security concepts, a widely used abstract model is employed, featuring Alice, Bob, and Eve. This model helps students understand how legitimate communication works, how it can be attacked, and why security mechanisms are necessary. Core Aspects of Network Security Computer network security focuses on protecting information as it is exchanged between interconnected systems. It is built upon four fundamental aspects: 1. Confidentiality Confidentiality ensures that information remains private.
  • If a sender encrypts a message, only the intended recipient should be able to decrypt and read it.
  • Unauthorized parties should gain no meaningful information, even if they intercept the data.
2. Authentication Authentication verifies the identities of communicating parties.
  • Both the sender and receiver must confirm who they are communicating with.
  • This prevents attackers from pretending to be trusted users or systems.
3. Message Integrity (Message Authentication) Message integrity ensures that transmitted data has not been altered.
  • The receiver must be able to detect any modification immediately.
  • This protects against tampering, insertion, or deletion of data during transmission.
4. Access and Availability Availability ensures that network services remain usable.
  • Legitimate users must be able to access systems and services when needed.
  • Security mechanisms should protect against disruptions that prevent normal operation.
The Security Actors: Alice, Bob, and Eve To explain security threats clearly, network security often uses three symbolic characters: Alice and Bob
  • Represent legitimate and trusted entities.
  • They may be real users, applications, network devices, or servers.
  • Their goal is to communicate securely and reliably.
Examples include:
  • A user accessing an online banking service
  • Two routers exchanging routing information
  • A client communicating with a web server
Eve
  • Represents the adversary or intruder.
  • Eve is not a specific person, but a model for any malicious entity attempting to interfere with communication.
Common Attacks Performed by Eve Eve can attempt several types of attacks on the communication channel between Alice and Bob: Interception and Eavesdropping
  • Eve listens to the communication to obtain confidential information.
  • This violates confidentiality.
Message Manipulation
  • Eve intercepts messages and modifies their contents.
  • She may delete messages or inject new, fake ones.
  • This breaks message integrity.
Man-in-the-Middle (Hijacking)
  • Eve positions herself between Alice and Bob.
  • All communication passes through Eve without their knowledge.
  • Eve can read, modify, or redirect messages freely.
Impersonation and Spoofing
  • Eve pretends to be Alice when communicating with Bob.
  • Bob believes the messages originate from Alice, even though they do not.
  • This undermines authentication.
Denial of Service (DoS) Attacks
  • Eve overwhelms Bob with excessive requests.
  • Often combined with spoofing techniques.
  • Bob becomes unable to respond to legitimate requests from Alice.
  • This violates availability.
Key Educational Takeaways
  • Network security exists to protect confidentiality, integrity, authentication, and availability
  • Legitimate communication must be protected from interception and manipulation
  • Attackers exploit weaknesses in trust, identity, and visibility
  • The Alice–Bob–Eve model provides a simple but powerful way to analyze security threats
  • Understanding attacker behavior is essential for designing effective defenses


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CyberCode AcademyBy CyberCode Academy