Firewalls & Encryption (SQA National 5 Computing Science): Revision Note

Firewalls

What is a firewall?

• A firewall monitors and controls incoming and outgoing network traffic based on a set of rules

• It helps protect a computer or network by filtering data to ensure only safe and legitimate traffic is allowed through

Purpose of a firewall

• Prevents unauthorised access to or from a network

• Blocks potentially harmful data such as malware or hacking attempts

• Helps maintain network security

Types of firewall

• Hardware firewall – built into a router or network device to protect the entire network

• Software firewall – installed on individual computers to protect a single device

• Attacks prevented by firewalls

  • Hackers trying to access private data

  • Malware or viruses entering through the network

  • Unauthorised connections to or from the system

Encryption

What is encryption?

• Encryption is a method of scrambling data before it is transmitted across a network so that it cannot be understood if intercepted

Why is encryption used?

• It helps to protect data from unauthorised access and ensures that only users with the correct decryption key can read the information

How it works

• The data (called plaintext) is converted into ciphertext using an encryption key

• The receiver uses the same or matching key to decrypt the ciphertext back into plaintext

• This means that even if data is intercepted, it cannot be read without the correct key

Example

• If an email is intercepted while being sent across a network, encryption ensures that it cannot be read without the correct key

• This idea is similar to how messages were encrypted using the Enigma machine during World War II

• Without the correct settings, the intercepted messages were meaningless