The Windows Firewall works like a filter between your PC and the internet, blocking or allowing connections depending on whether or not they’re safe.

Firewalls will block or allow a lot of traffic automatically, but sometimes you may see a message asking you if you want to allow a program to connect to the internet. This usually happens when you use a new program for the first time.

Not sure if your firewall is running? Learn how to switch on the Windows Firewall.

There may also be situations where you need to allow a program through your firewall that has been blocked incorrectly - known as whitelisting.

Whitelisting with the Windows Firewall

To manage the whitelist in the Windows Firewall, click Start, type firewall and click Windows Firewall. Click Allow a program or feature through Windows Firewall (or, if you’re using Windows 10, click Allow an app or feature through Windows Firewall).

On the next screen, click Change settings, then tick or untick the box next to an item to allow or block it.

Alternatively, you can tick or untick the box in either the Private or Public columns. Say, if you wanted to allow a program internet access when you’re connected to your home network (Private), but block it when you’re connected to a public one, such as a wi-fi hotspot.

Block all incoming programs

There are occasions where it’s much safer to block all incoming data connections to your computer, including all of the programs on your ‘whitelist’ of connections that you’d normally allow. For example, you may wish to do this if you’re using an unsecured wi-fi connection in an airport or hotel, where malware could potentially gain access to your laptop through open connections.

To disallow all incoming data connections with the Windows Firewall, click Start, type firewall and click Windows Firewall > Change notification settings. Under Public network settings, tick Block all incoming connections, including those in the list of allowed programs, then OK.

With this setting enabled, you’ll still be able to send and receive email and browse the web, but other connections will be blocked automatically.