What a firewall does, and what it does not

A firewall sits between your network and the internet, and between parts of your own network. It looks at the traffic trying to pass and decides, by rules, whether to allow it.

What it does well

• Blocks connections that nobody inside asked for, so that services on your network are not open to the whole internet.
• Lets you separate parts of the network, for example guests, staff and the accounts system.
• Records what was blocked and allowed, which helps when something looks wrong.
• Provides protected remote access, so staff can work away from the office.

What it does not do

• It cannot stop a person from typing their password into a fake page.
• It does not protect a laptop that is taken home and used on another network.
• It does not fix software that has not been updated.
• It does not help if the rules are too open, which happens often when nobody reviews them.

Questions worth asking about yours

1. When were the rules last reviewed, and by whom?
2. Is the firewall software kept up to date?
3. Are guests on a separate network?
4. Who receives the alerts, and who acts on them?
5. Is there a written copy of the settings, so a replacement can be set up quickly?

A firewall is one layer. It works best next to protected devices, a second sign-in step, tested backups and people who know what a suspicious message looks like.