Whenever you buy network appliances, it is not obvious that all of them have firewall features. And to deal with these issues you can buy firewall security products with it. You can get advance security procedure and port blocking to keep your network secure.
Without Firewall, What Kind of Things can happen?
Suppose, if you have installed fresh Windows on your computer and you forgot to unpatched it. Your computer will be for sure attacked within few minutes. Open ports could be the source of attack and can bomber on your computer with popup messages like viruses, worms and Trojans. These attacks automatically load behind your back, to deal with these issues people use Spyware and Malware, which can block your browser. A company conducted an experiment, in which they left an unpatched computer free to use, and after 2 and half hour, the computer was not able to work. When they used the firewall on that computer, they were able to protect the PC from number of attacks.
Even if you have all of the latest service packs of Windows, and you are not using any firewall security in your systems then it means anyone can attack your system. Viruses, worms and Trojans love to attack those computers and systems that have unprotected and open portal.
Now How Firewall Security Works?
Almost all of the firewalls like you have one in windows helps to alert and protect you from incoming attacks. If anyone attack your computer will first have to face firewall security. The first thing that firewall does is to deflect the attacks and warn you about the present or more incoming attacks. You can also buy Cisco firewall security device, which is best in alarming the doubtful incoming and outgoing traffics (which is not present in basic firewall securities). So best firewalls, like this one warn you about both outgoing and incoming traffics.