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1. MAN 2102 - COMPUTER
NETWORKING AND INTERNET
Program : HNDM YEAR II, SEMESTER I
Lecturer : D.Dhinesh melroy
[BSc (hons) in Information Technology]
Designation : Visiting Lecturer, SLIATE
Advanced Technological Institute
Dehiwala
Higher National Diploma in Management

2.  A LAN is a network that is used for communicating among computer
devices, usually within an office building or home
 LAN’s enable the sharing of resources such as files or hardware devices that
may be needed by multiple users
Is very fast, with speeds from 100 Mbps to 10 Gbps
Introduction to Local Area Network

3. Introduction to Local Area Network

4.  A network connecting two or more geographically separate locations.
 Wide area network (WAN) involves a carrier or network service provider
(NSP) to make the connectivity.
Introduction to Wide Area Network

5. What is the difference between LAN and WAN?

6.  Network Security refers to protecting data and resources from
unauthorized access or attacks.
Example:
Protecting your personal data (like passwords) from hackers while using the
Internet.
 Data Security
Data Security means protecting digital information from unauthorized
access.
Example:
Online banking systems use encryption to protect transaction data.
Introduction to Network Security

7.  Types of Security Threats
1. Viruses
2. Worms
3. Trojan Horses
4. Phishing
5. Spyware
Introduction to Network Security

8.  Viruses
A virus is malicious code that attaches itself to a legitimate program or
file and runs when the host is executed. It requires human action (open/run) to
spread.
Common symptoms:
Slow system, unexpected crashes, corrupted files, missing files,
unknown email sent from user’s account.
Introduction to Network Security

9.  Prevention
1. Keep antivirus signatures updated
2. Do not open unknown attachments
3. Scan external drives before use
 Example:
ILOVEYOU (2000)
[Infected File.exe] => (shared via USB/email) => [User A opens file] =>
[Virus executes] => [Infects files on A] => [Sends infected file to A's contacts]
Introduction to Network Security

10.  Worms
A worm is standalone malware that self-replicates and spreads over
networks without needing to attach to a host file or require human action.
Common symptoms:
Network slowdown, spikes in outbound traffic, many similar processes
running, many identical files on systems.
Introduction to Network Security

11.  Trojan Horses
A Trojan is malware disguised as useful or harmless software; once run
it performs malicious actions (backdoor, keylogger) but does not self-replicate.
Common symptoms:
Unknown remote connections, new user accounts, files modified by
unknown process, strange outgoing traffic.
Introduction to Network Security

12.  Phishing
Phishing uses deceptive emails, messages, or websites to trick users into
revealing credentials, financial data, or installing malware.
Common symptoms:
Unexpected requests for credentials, odd-looking URLs, requests to
provide sensitive info immediately, poor grammar in the message.
Introduction to Network Security

13.  Prevention
1. Train users to check sender addresses and hover over links
Example:
An email appearing to be from “bank.com-support” asking to reset
password and stealing credentials.
[Attacker crafts email] => [Sends to victim] => [Victim clicks link] =>
[Fake login page] => [Victim enters credentials] => [Attacker collects
credentials]
Introduction to Network Security

14.  Solution for Internet Threats
1. Use Antivirus Software
2. Install Firewalls
3. Keep Systems Updated
4. Use Strong Passwords
5. Enable Encryption
6. Regular Backups
Introduction to Network Security

15.  Encryption
Process of converting plain text into coded (cipher) text.
Example:
Plain text → “HELLO”
Encrypted → “J*N#N@Q”
Introduction to Network Security

16.  Decryption
Converting cipher text back into plain text.
Example:
Cipher text → “J*N#N@Q”
Decrypted → “HELLO”
Introduction to Network Security