Wireless networks are convenient, but radio signals travel beyond walls and can be received by anyone nearby. This lesson covers how Wi-Fi works and how to defend networks you own or manage.

How wireless networks work

Wi-Fi (IEEE 802.11) uses radio frequencies, mainly 2.4 GHz, 5 GHz and now 6 GHz bands. A wireless access point (WAP) connects wireless devices to the wired network. The network name is the SSID.

  • 2.4 GHz: longer range and better wall penetration, but slower and more crowded.
  • 5 GHz and 6 GHz: faster and less congested, but shorter range.
  • Wi-Fi is a shared medium, so many devices compete for airtime, and interference from other networks or appliances reduces speed.

Other wireless technologies include Bluetooth (short range) and mobile data (4G/5G cellular).

Wireless security threats

Because the signal travels through the air, risks include:

  • Eavesdropping: capturing unencrypted traffic.
  • Unauthorised access: someone joining a network with a weak password and using or monitoring it.
  • Rogue or fake access points: an attacker-run hotspot imitating a legitimate name to trick users.
  • Weak configuration: default passwords, outdated encryption.

Defending a wireless network

On a network you own or administer, apply these measures:

  • Use strong encryption. WPA3 is the current standard; WPA2 with AES (WPA2-AES) is acceptable. The old WEP and WPA/TKIP are broken and must not be used.
  • Use a long, unique passphrase for Wi-Fi, and change the router’s default admin password.
  • Keep router firmware updated to fix known vulnerabilities.
  • Disable WPS (Wi-Fi Protected Setup), which has known weaknesses.
  • Use a guest network for visitors and IoT devices, separate from main devices.
  • Enterprise networks use WPA2/WPA3-Enterprise with individual logins (802.1X) rather than a shared password.
  • Firewall: filters incoming and outgoing traffic by rules, either as hardware or software.
  • Authentication and MAC filtering: MAC filtering is a weak extra layer only, since addresses can be copied.
  • On public Wi-Fi, use HTTPS sites and a trusted VPN, and avoid sensitive tasks.

Hiding the SSID is not real security. Encryption and strong passphrases are what protect the network.

Encryption in brief

Encryption converts readable data (plaintext) into unreadable ciphertext using a key, so intercepted wireless traffic is useless without the key.

Check your understanding

Which Wi-Fi security standard is currently recommended?

  • WEP
  • WPA3
  • Open network
  • WPS only

Answer: WPA3. WEP is broken and open networks give no protection.

Why is the 5 GHz band often faster but shorter range than 2.4 GHz?

  • It uses a higher frequency that carries more data but penetrates obstacles less well
  • It uses cables
  • It is encrypted
  • It is older

Answer: It uses a higher frequency that carries more data but penetrates obstacles less well. This is a trade-off between speed and range.

What is a rogue access point?

  • A fake or unauthorised access point
  • A fast router
  • A backup server
  • A strong password

Answer: A fake or unauthorised access point. It can trick users into connecting.

What does a firewall do?

  • Filters network traffic according to rules
  • Cools the router
  • Increases bandwidth
  • Stores backups

Answer: Filters network traffic according to rules. It blocks unwanted connections.

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