Network security methods

Network Security Methods

No single security measure can fully protect a network. Effective network security uses several methods together, each addressing a different type of risk. The four methods you need to know are authentication, encryption, firewalls, and MAC address filtering. Each can be used independently, but they are most effective when layered together.

The Four Security Methods

Authentication

Authentication is the process of verifying that someone or something is who or what they claim to be before granting access to a network or system. It answers the question: "Are you who you say you are?" Common authentication methods include:

  • Username and password: the most common form. A user provides credentials that must match records stored on the system.
  • Two-factor authentication (2FA): requires a second proof of identity in addition to a password - such as a code sent to a mobile phone. Even if a password is stolen, the attacker cannot log in without the second factor.
  • Biometrics: uses physical characteristics such as a fingerprint or face scan to verify identity.
Username + Password Check credentials ✓ Access granted ✗ Access denied

When used: logging into a school network, accessing online banking, unlocking a smartphone, connecting to a corporate VPN. Any system where only authorised users should have access requires authentication.

Encryption

Encryption is the process of converting data into a scrambled form (called ciphertext) using a mathematical algorithm and a key, so that it cannot be read by anyone who intercepts it without the correct decryption key. Even if an attacker captures encrypted data in transit, they cannot read it without the key.

Plaintext Hello! 🔑 key Ciphertext X#4! intercepted - unreadable ✗ Ciphertext X#4! 🔑 key Plaintext Hello!

Data intercepted in transit is unreadable without the decryption key.

When used: HTTPS websites (encrypting web traffic), messaging apps (end-to-end encryption), email encryption, storing passwords in databases (hashing is a related one-way process), and encrypting files on a storage device.

Firewall

A firewall is a network security device (hardware, software, or both) that monitors incoming and outgoing network traffic and decides whether to allow or block specific traffic based on a defined set of security rules. Firewalls sit between a trusted internal network and an untrusted external network (such as the internet), acting as a gatekeeper. Modern firewalls have evolved significantly and can examine traffic in detail - inspecting packet contents, tracking connection states, and blocking suspicious behaviour patterns - not just filtering by address or port number.

Internet ✓ allowed ✗ blocked Firewall checks rules ✗ Internal network

The firewall allows legitimate traffic and blocks traffic that breaks its rules, protecting the internal network.

When used: placed at the boundary between an internal network and the internet in almost every organisation and home router. Software firewalls can also run on individual devices to filter traffic for that specific machine.

MAC Address Filtering

Every network adapter (the hardware component that connects a device to a network) has a unique identifier permanently embedded in it at manufacture, called a MAC address (Media Access Control address). MAC address filtering allows a network administrator to specify which MAC addresses are permitted to connect to the network - devices with addresses not on the approved list are blocked, even if they know the Wi-Fi password.

WAP Approved: AA-BB-CC... Device A MAC: AA-BB-CC ✓ allowed Device B MAC: 99-88-77 ✗ blocked MAC: AA-BB-CC is approved. MAC: 99-88-77 is not.

Only devices whose MAC address appears on the approved list can connect, regardless of whether they know the password.

When used: controlling which devices can join a school or office Wi-Fi network; restricting access in environments where known, trusted devices should be the only ones permitted to connect. MAC filtering is most effective as an additional layer alongside a strong password, not as a standalone measure.

Layered Security: Methods Working Together

Each security method addresses a different aspect of network protection. Using them together provides far stronger security than any single method alone:

  • Authentication ensures only known users can log in.
  • Encryption ensures that data intercepted in transit cannot be read.
  • Firewall blocks unauthorised traffic from entering or leaving the network.
  • MAC address filtering restricts which physical devices can even attempt to connect.

A school network using all four methods requires an attacker to: connect a device whose MAC address is approved, pass the firewall's traffic rules, authenticate with valid credentials, and decrypt any data they intercept. Each layer closes a different vulnerability. This principle - using multiple overlapping measures - is called defence in depth.

 Key Takeaways

  • Authentication verifies the identity of users before granting access. Strong authentication uses multiple factors.
  • Encryption scrambles data so it cannot be read by anyone who intercepts it without the decryption key.
  • A firewall monitors incoming and outgoing network traffic and allows or blocks it based on defined rules.
  • MAC address filtering controls network access based on the unique physical address embedded in each device's network adapter.
  • Security methods are most effective when layered together - each closes a different vulnerability that the others leave open.