Chapter 1: Fundamentals of Network Security¶
What Is Network Security?¶
Network security is the protection of network communications from:
Unauthorized access
Abuse or misuse
Damage or disruption
It includes monitoring traffic, blocking unsafe activity, and responding to threats.
Core Security Principles¶
Confidentiality¶
Protects data from being seen by unauthorized users. Only people with a valid need to know should have access.
Integrity¶
Protects data from being changed improperly. Ensures data remains accurate and consistent.
Availability¶
Ensures systems and data are accessible when needed. Protects against downtime and data loss.
Authentication¶
Verifies who a user is. Examples: passwords, biometrics, multifactor authentication (MFA).
Nonrepudiation¶
Prevents users from denying actions they performed. Often provided through encryption and digital signatures.
Security Policies¶
A security policy defines:
What is allowed
What is not allowed
How security is enforced
Policies keep security organized and effective.
Network Fundamentals¶
TCP/IP¶
Most networks use TCP/IP.
Two versions of IP:
IPv4 – most widely used today
IPv6 – newer and growing in use
OSI Model¶
The OSI model explains how network communication works using seven layers.
Layer |
Function |
|---|---|
7 |
Application – User programs |
6 |
Presentation – Format data |
5 |
Session – Manage sessions |
4 |
Transport – Send data |
3 |
Network – IP and routing |
2 |
Data Link – MAC addresses |
1 |
Physical – Bits and signals |
Addresses¶
Logical Addresses (IP)¶
Identify devices globally
Unique across the Internet
Not tied to physical hardware
Allow communication between any two hosts
Physical Addresses (MAC)¶
Identify devices locally
Unique only on the local network
Assigned by the NIC manufacturer
Tied to hardware but can be spoofed
MAC Address Spoofing¶
MAC addresses can be changed using:
Linux, Unix, macOS commands
Windows tools (SMAC, MAC Changer, etc.)
Network Security Components¶
Nodes and Hosts¶
A node is any device on a network (PC, printer, server).
A host is a node with an IP address that provides or uses services.
Firewalls¶
A firewall filters network traffic. It blocks harmful or unauthorized connections.
VPN (Virtual Private Network)¶
A VPN creates an encrypted tunnel across the Internet. Used for secure remote access.
Proxy Servers¶
A proxy sits between users and the Internet.
It:
Filters traffic
Hides internal addresses
Adds security and privacy
DNS¶
DNS converts names into IP addresses.
Example:
www.example.com → IP address
DNS must be protected but does not secure the network itself.
Intrusion Detection & Prevention¶
IDS detects attacks. IPS detects and blocks attacks.
They can:
Alert admins
Block IPs
Close ports
Stop connections
Network Access Control (NAC)¶
NAC checks devices before allowing them on the network.
It ensures systems have:
Antivirus
Security patches
Firewalls
Authorization
Non-compliant devices can be blocked.