The Danger: Malicious users may locate and attempt to break into your computer from the Internet.
The Cause: All computers that communicate over the Internet must have a valid IP address, such as 61.232.252.6. These addresses allow computers to exchange data with other computers over the ‘net. Your system also leaves a variety of ports open to listen for incoming data. Ports are access points for certain kinds of data to enter and leave your computer. For example, while you are viewing this website, your computer and our web server are communicating through port 80, the default port for the HTTP language that web pages generally use.
The trouble is that anyone can use freely available software like GFI’s LANguard security scanner to scan a range of IP addresses for computers and gather information about these systems. If your computer is poorly password protected these utilities provide remote users with the ability to directly access your files.
This happens because by default, many ports in your system are fully prepared to listen and respond to any data request from the Internet. This means that your system is fully visible, the equivalent of wearing glow-in-the dark clothes in a blackout…
The Cure to Step 2.
The cure: Use a firewall program or device.
A firewall is a software program or hardware device which blocks remote access to your computer. It does this by closing all ports to data unless the communication is initiated from inside the firewall first. So, you could, for example, surf this page without problems through a firewall since your computer sends the request for data to our web server first.
The firewall would note the Internet address that your request was sent to and allow return communications from that specific address back through the firewall. However, anyone trying to scan a range of IP addresses for vulnerable computers would turn up a blank for your address, since the firewall blocks all unsolicited communication from the Internet.
Almost all home Internet sharing devices include firewalls, so if you are using a router to share your Internet connection within your home, you are likely already protected. Otherwise, you need to use a software firewall. Windows XP comes included with one, though you need to activate it. Several free third-party software firewalls are also available, most notably Zone Lab’s Zonealarm.
To activate the Windows firewall, go to ‘start/control panel/network and Internet connections/network connections’ then right click on your Internet connection and select ‘properties’.
Go to the ‘advanced’ tab and check the ‘internet connection firewall’ box.
The windows firewall is now active and will block most non-requested data from entering your system.
Unless you have another form of firewall software like Zonealarm installed, the XP firewall should be active by default.
To use Zonealarm first download and install the software.
Go to ‘alerts and logs’ and change the ‘alert events shown’ setting to off. This is just to prevent the program informing you every time it blocks data remotely.
The main advantage of Zonealarm over the Windows firewall is its ability to block data coming from inside your system out to the Internet. This enables it to catch Trojan horse viruses and spyware in the act and prevent them from sending privacy and security compromising data from your system. Zonealarm will pop up a permission box every time a program attempts to access the Internet.
If it’s a recognized program like IE, you can allow it permanent access by checking ‘yes’ and ‘do not ask this question again.’ Otherwise, you can go to the ‘program control/programs’ window within Zonealarm and manually set which applications can access the Internet.
My Recommendation: Windows Firewall is much more capable than it once was. If you have 1 or 2 computers and never travel with them, Windows Firewall in combination with your internet router is fine.
If you have more than 2 computers on your network, it is probably a good idea to use something easier to configure and understand or use me to configure and monitor your firewall.