Network Security

🔺 The CIA triad

Network security protects three things. Confidentiality: only authorised people can read the data. Integrity: data is not changed without permission. Availability: systems and data are there when they are needed. Every threat attacks at least one of these, and every control protects at least one.

⚠️ Common threats

Malware: viruses, worms, trojans and ransomware, which locks files for payment. Phishing tricks people into giving away passwords or PINs. Denial of service (DoS, or DDoS from many machines) floods a service until it stops. Eavesdropping, or man-in-the-middle, intercepts data, often on open Wi-Fi. Weak passwords and careless insiders cause many breaches too.

🛡️ Technical controls

A firewall filters traffic using rules, blocking what isn't allowed. An intrusion detection system (IDS) watches for attack patterns and raises alerts. Encryption scrambles data so only the right key can read it: HTTPS for websites, WPA2 or WPA3 for Wi-Fi. Antivirus and anti-malware find and remove malicious software.

🔑 Access control

Give each user their own account with only the access they need (least privilege). Require strong passwords, and add multi-factor authentication, such as a code sent to your phone. Remove accounts when people leave. Keep server rooms and network equipment physically locked.

🔎 Keeping it secure

Install software updates promptly; they patch known weaknesses. Back up important data, offline or in a separate place, so ransomware can't hold you hostage. Audit and review logs to spot unusual activity. Train users to recognise phishing. In Kenya, the Computer Misuse and Cybercrimes Act (2018) makes unauthorised access to computer systems a crime.

Key points

• Security protects confidentiality, integrity and availability: the CIA triad.
• Threats include malware, phishing, denial of service and eavesdropping.
• A firewall filters traffic; an IDS watches for attacks.
• Encryption, like HTTPS and WPA3, keeps data private.
• Give each user only the access they need, with strong passwords and multi-factor authentication.
• Update software, back up data, and review the logs.
• Kenya's Computer Misuse and Cybercrimes Act makes unauthorised access a crime.

Try it for real: Secure a network

• Check your home or school Wi-Fi settings (with permission): is it using WPA2 or WPA3, and has the router's default admin password been changed?
• Write three password rules you would set for your school's computers, and explain which part of the CIA triad each protects.