Security measures and protecting data
Defending data
- Knowing the threats, we now build the defences.
- The right measure depends on the threat — encryption for interception, authentication for access.
- At the core sits encryption: turning readable data into a locked form.
Security measures
- Standalone PC — strong password, up-to-date antivirus, prompt software updates, backups, full-disk encryption, locked screen.
- Networked PC — all of the above, plus a firewall, per-user permissions (admin rights only for admins), and audit logs.
- Across the internet — a VPN (encrypts traffic to the gateway), HTTPS/TLS for web traffic, and intrusion detection.
A firewall mainly:
A firewall controls which network traffic is allowed in or out, by a set of rules.
HTTPS/TLS protects web traffic by:
HTTPS encrypts the traffic so anyone intercepting it sees only ciphertext.
Matching the measure to the threat
- Interception in transit → encrypt the data (HTTPS, VPN) — intercepted ciphertext is useless without the key.
- Unauthorised access → strong authentication (long passwords, two-factor), authorisation, lock-out after failed logins.
- Malware → antivirus + patching; phishing → user training + email filtering.
- Internal threats → the least-privilege principle (give each user only what they need) + auditing.
The best defence against data being intercepted in transit is to:
Encrypted data intercepted in transit is useless without the key. Authentication and antivirus address different threats.
The least-privilege principle means:
Limiting each user to the minimum access needed reduces the damage from mistakes or insider threats.
Encryption
- Encryption turns plaintext into ciphertext using a key.
- Symmetric (AES) uses one shared key for both encrypting and decrypting — fast, but the key must be shared safely.
- Asymmetric (RSA) uses a public key (to encrypt) and a private key (to decrypt) — solves key sharing.
- It protects data at rest and in transit.
Asymmetric encryption (e.g. RSA) differs from symmetric (e.g. AES) because it:
Asymmetric uses a public/private key pair (solving key sharing); symmetric uses one shared key (fast).
Authentication
- Verify the user by something they know (password), have (token, phone), or are (fingerprint).
- Two-factor authentication (2FA) combines two of these — much stronger than a password alone.
- Combine with access control (file permissions) and backups for defence in depth.
A code from a phone app is an example of which authentication factor?
A token/phone code is "something you have". Two-factor combines it with a password ("know") or biometric ("are").
You've got it
- layer defences: password/antivirus/updates/backup/encryption → + firewall/permissions/audit → + VPN/HTTPS
- match measure to threat: interception → encrypt, unauthorised access → authentication/2FA, internal → least privilege
- symmetric = one shared key (AES); asymmetric = public + private key (RSA)
- authentication = something you know / have / are; 2FA combines two