Network security

The essentials

Network security protects data and devices on a network from unauthorised access, misuse and damage. It combines tools such as firewalls and antivirus software with safe practices by users.

Key points

• Firewall: hardware or software that monitors incoming and outgoing network traffic and allows or blocks it according to a set of security rules. It stands between a trusted internal network and an untrusted network such as the Internet. A personal firewall protects one computer; a network firewall protects a whole network.
• Cookies: small text files stored by websites in the browser. They make browsing convenient (remembering logins and carts) but can be misused for tracking, so users should manage or clear them, especially on shared computers.
• Antivirus software: detects and removes malware. It compares files with signatures (patterns) of known malware and also watches for suspicious behaviour. Its signature database must be updated regularly to catch new threats.
• Hackers: people who find and use weaknesses in computer systems. Ethical (white hat) hackers do this with permission to find and fix security flaws.
• Crackers (black hat hackers): break into systems illegally with malicious intent, such as stealing data or causing damage.
• HTTP vs HTTPS: HTTP sends data as plain text, so it can be read if intercepted. HTTPS encrypts data using SSL/TLS and verifies the website's identity with a digital certificate. Browsers show a padlock symbol for HTTPS. Sensitive data such as passwords and card numbers should be entered only on HTTPS sites.

Exam tips

• Firewall = filter traffic by rules; antivirus = detect and remove malware already on the device.
• White hat and black hat differ by permission and intent, not by skill.

Common mistakes

• Thinking a firewall removes viruses from infected files.
• Thinking HTTPS guarantees that a website is honest; it secures the connection, not the site owner's intentions.