Classroom Notes: 3.2 Data Transmission and Security

Data is transmitted over a network using packet switching:

• The message is broken into small packets.
• Each packet carries address + data.
• Packets travel independently across the network.
• At the destination, they are reassembled into the original message.

Echo check is an error-detection method:

• Sender transmits data.
• Receiver immediately echoes it back.
• Sender compares echoed data with the original.
• If they match → data is correct.
• If not → an error occurred, and sender resends the data packet.

A firewall is a security barrier that controls incoming and outgoing network traffic based on rules.

• Function: Blocks unauthorized access, allows safe communication, and protects against threats.
• Types of Firewalls:
  • Hardware Firewall: A physical device placed between the network and the Internet; often used in organizations for strong, centralized protection.
  • Software Firewall: A program installed on individual computers; monitors and filters traffic on that device.

A computer virus is a malicious program that can copy itself and spread to other files or systems.

• It disrupts normal functions of a computer, and damages data.
• Like a biological virus, it needs a “host” (software or file) to multiply.

Antivirus software is a program that protects computers from malicious software (like viruses, worms, and trojans).

• Function: It scans files and programs, detects harmful code, removes or quarantines threats, and prevents infections.
• It works continuously in the background to keep the system safe.

Spyware is malicious software that secretly monitors a user's activities.

• It collects information like keystrokes, browsing habits, or personal data.
• It is often installed without the user's knowledge.

Antispyware is software designed to detect, block, and remove spyware.

• It scans the system for hidden spyware programs.
• Prevents unauthorized monitoring of user activity.
• Protects sensitive data like passwords and personal information.