A firewall protects your PC against hackers by closing the ports you do not use. Since many programs use Internet communications, PCs use program-assigned port numbers so that they can distinguish among the communications of the various programs.
PC ports open to the Internet
Most PCs are, by default, set up with all their ports open to the Internet. This setup allows hackers to attack your PC without your authorisation. All you have to do to allow this is enable your Internet connection.
These attacks mostly occur through small, fully automatic programs, called worms, that exploit undiscovered or unclosed security holes in your programs and spread themselves to PCs on the Internet without the hacker’s active participation. After a successful attack, a worm can for example inform the hacker that there is yet another PC ready for the hacker to exploit.
Firewalls reduce the risk of worms
Since a firewall closes the ports you do not need, it efficiently limits the number of programs in which a worm can exploit security holes. Most firewalls can also easily be closed to block all communications through the Internet. For the hacker, it’s as though the PC were turned off. Use this function even when you do not plan to go on the Internet, as this reduces the time available for an attack to a minimum.
Many good firewall programs are available for private use free of charge.
Updating a firewall
Firewall software also needs to be upgraded once in a while (although not as often as antivirus software). Once the update is downloaded, the program will typically have to be closed for a short time and reopened for the update to be implemented. During this time, your PC may be unprotected if it is still connected to the Internet. We recommend that you close your connection when upgrading your firewall. Most firewall upgrades will tell you when the critical period begins.
We highly recommend that you use firewall software to protect your PC and on the internet you can find more info about software and suppliers.