Firewalls are hardware or software security systems designed to prevent unauthorized access to or from your computer or private network.

Firewall diagram

Firewalls are located between the user's computer and the external network and filter incoming and outgoing traffic according to the established rules.

Firewall rules can be based on:

  • IP-addresses
  • Domain names
  • Protocols
  • Programs
  • Ports
  • Key words

The firewall software will alert the user when unknown or new software tries to access external data sources.

In short, firewalls are an essential tool in the fight against hackers and malware.

Most operating systems include a firewall.

Functions of firewalls:

  • Packet filtering 
  • Stop hackers from accessing your computer.
  • Protect your personal information.
  • Blocks “pop up” ads and certain cookies.
  • Determines which programs can access the internet.
  • Block invalid packets.

Packet filtering (Static Filtering)

  • Controls network access according to network administrator rules and policies.
  • It examines the source and destination IP addresses in packet headers.
  • If the IP addresses match those recorded on the administators 'permitted list' they are accepted.
  • It can block packets based on the protocols being used and port numbers being accessed.


1. Explain why we use firewall.

2. Name three functions of firewall.


Ex. 1 (Prepared by Sabina, Rimma, Elaman, grade 12, group 1, 2021)

Exam questions:



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