A firewall is used to control incoming and outgoing traffic. Many users believe that simply installing a firewall is enough to protect their computer from malicious attacks but that does not have to be the case.
An improperly configured firewall can do more damage than harm, or at least leave some attack vectors open that would be closed if it had been configured properly.
It is often a good idea to simply test the firewall for open ports. You see, ports are used for connections and only open ports can be used to connect to the PC. Common ports are port 80 for http connections (that's web traffic using a browser usually) or port 21 for ftp connections. It does not make sense to have port 21 open if no ftp server is operated on the computer for example.
Shields UP is a free Internet service that can test ports on the local system. Users just need to open the https://www.grc.com/x/ne.dll?bh0bkyd2 url in their web browser to load the configuration window and click on the proceeed button to get started.
From there is it just a matter of selecting one of the available tests, e.g. for file sharing ports, common ports or custom ports to get a list of results immediately afterwards.
The first three available tests are probably the most interesting. File Sharing tests for open file sharing ports, Common Ports the most common, popular and targeted ports, and all services ports the first 1056 ports of the system.
Each port is reported back as open, closed or stealthy. Open means that the port is accessible from remote locations, closed that is is not and stealthy that a port is blocked somewhere between the computer and the Internet, for instance by a router.
It is then up to the user to react on the results. The information posted on the test website offer a good starting point to get things sorted out.
If you notice open ports for instance and come to the conclusion that they are not required, you should close them on your system. How that is done depends on the operating system used which often requires more research on your part.
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Ghacks is a technology news blog that was founded in 2005 by Martin Brinkmann. It has since then become one of the most popular tech news sites on the Internet with five authors and regular contributions from freelance writers.