Edexcel IGCSE ICT
Securing Data on a Network
Big idea: because networks are constantly under attack from people who want to steal, damage, or spy on data, we layer up several different tools — passwords, firewalls, encryption, VPNs, permissions, and logs — so that even if one layer fails, the data is still protected.
Summary — The Whole Chapter in One Glance
- Usernames & passwords — authenticate who you are, stored encrypted so even a stolen database is useless.
- Firewalls — hardware or software barriers that filter traffic between a network and the internet.
- Encryption — scrambles data using keys and algorithms so it's meaningless if intercepted. Two types: symmetric (one shared key) and public key (two keys: public + private).
- WEP vs WPA — two wireless encryption protocols. WEP uses one shared key for everyone (weak); WPA gives every device its own key and changes it constantly (strong).
- VPNs — create an encrypted "tunnel" so you can safely connect to a private network remotely.
- File access rights — Read / Write / Delete / Execute permissions control exactly what a user can do to a file.
- Transaction logs & backups — logs record what happened (for monitoring, not prevention); backups are copies kept safe in case data is lost or corrupted.
1. Usernames & Passwords
How does a password actually help?
Think of a password as a digital lock on a door. The "door" is your account, and anyone without the right key (password) simply cannot get in. But it does more than just block strangers — it's the way the system checks you are who you say you are. This checking process has a proper name: authentication.
Here's the part that trips a lot of students up: passwords are not stored as the plain text you typed. If a company stored "password123" directly in their database and a hacker broke in, every single user's password would be instantly readable. Instead, systems store passwords as encrypted/ciphered text. So even if a hacker steals the entire database, all they see is scrambled nonsense — they still can't log in as you.
Analogy: Imagine a nightclub bouncer who doesn't remember your face, but remembers a secret scrambled version of your ID number. You give your real ID, the bouncer scrambles it the same way, and checks if it matches the scrambled version on the list. Even if someone steals the bouncer's list, all they get is scrambled numbers — not usable ID numbers.
Key Rule
Strong passwords + regular password changes = the two habits that keep an account genuinely secure over time.
Common Mistake
Students often write "passwords are stored so hackers can't see them" — too vague for full marks. Always say
WHY: they're stored encrypted so that even with unauthorised access to the database, the hacker cannot read the individual passwords.
Practice Question
Explain why passwords are stored in an encrypted format rather than as plain text. [2]
2. Firewalls
What is a firewall?
A firewall is a barrier that sits between your network and the internet. Every request trying to get in — or trying to get out — passes through the firewall first, which checks whether the traffic is legitimate before letting it through. Anything suspicious gets blocked.