What is Firewall?

In plain English

A firewall is like a security guard on the door of your computer or network. Every bit of information trying to get in or out has to pass the guard first. The firewall checks whether it's allowed — and if something looks wrong or wasn't invited, it's turned away before it can cause harm.

You already have one. Windows comes with a built-in firewall (it's switched on by default), and your home internet box has one too. Most of the time it works quietly in the background, and you'll never notice it doing its job.

Why it matters

Your devices are connected to the internet, which means they can be probed by automated attacks looking for a way in — even if nobody is specifically targeting you. A firewall is the first line of defence that blocks those uninvited connections. For a small business, it also helps stop a problem on one computer from spreading to the others on your network. It's not the whole picture (you still need good antivirus and sensible habits), but switching it off would leave a door wide open.

What to do

• Leave it switched on. On Windows, the firewall is on by default — the safest thing you can do is leave it that way. You can check under Settings, then Privacy & security, then Windows Security, then Firewall & network protection.
• Be cautious with "allow" pop-ups. If an app asks to be let through the firewall, only say yes if it's software you recognise and just installed. If you're not sure, say no — you can always allow it later.
• Don't turn it off to fix a problem. Some guides tell you to disable the firewall to get something working. That's almost never the right answer, and it's easy to forget to turn it back on.
• You don't usually need to buy extra. For most homes and small offices, the firewall built into Windows and your router is plenty.

How 365 Techies can help

If you'd rather not fiddle with security settings yourself, we're happy to check your firewall and overall protection are set up sensibly — for homes and small businesses across Bournemouth, Poole, Christchurch and Dorset.

Related: Router · Malware · IP address · Operating system — or browse the full A–Z jargon buster.