Computer firewalls can help to ensure that unauthorised people or computers can't access your computer over the network.
Computer firewalls check the information that is coming into your computer from the internet/network and either block it or allow it to pass on to your computer. You only need one firewall on your computer. If you have any more, they will conflict with each other!
Firewalls are normally available as part of the operating system, but is yours turned on?
To find out how to check your own personal computer see information for