These days computer security is very important due to extensive use of Internet. People who use shareware and freeware software and utilities need to be very sure about their computer's security. A firewall is a software package that keeps track of any internet traffic pieces that go in and out of your computer.
For your computer to be on the internet, it has an IP address, say 126.96.36.199. When you go to a website, you are in essence saying to another computer,
"Hello, computer 188.8.131.52, I am computer 184.108.40.206. Please send me some information" Then computer 220.127.116.11 sends information (a webpage, say) to computer 18.104.22.168 and your computer gets it and processes it. So all computers talk to each other by knowing their addresses. Sort of like letters going to peoples' mailboxes. But this is done in real time.
Anti-virus software is one form of protection against wrongdoing. Virus software watches your incoming mail for viruses and sometimes anything you download from Internet too. Anti-virus software is KEY if you are downloading shareware programs, to make sure they are not virus-laden. But what if something gets onto your system not by mail or downloading it?
Because your computer has an address - 22.214.171.124 - anyone out there who has a random "scanning program" can find you eventually. There are people with machines that do nothing but going around trying every IP address combination and seeing what they find there. So as you are on line right now reading this message, your computer is on the internet, and it has a valid address. We'll say it is 126.96.36.199. And a hacker at this very moment could look at his computer screen and say "Aha! Computer 188.8.131.52 is on line! Let's see what I can do over there!"
The hacker then runs a series of attacks against machine 184.108.40.206 to see if they can get in. Your virus software knows nothing about this, there aren't any mail messages coming in because of the attack. Instead, the hacker is trying to send various requests to machine 220.127.116.11 through known security holes to try to get to your hard drive. Without a firewall and fully up to date updates, the hacker could easily get in. And then they start putting MP3s on your hard drive, or whatever, and telling his friends that your 18.104.22.168 machine is their new "storage location" for illegal files. They could put a piece of bad code onto your system that then reports back to them when you do various activities. So now your machine is sending them information when you do things.
Firewalls watch for both incoming and outgoing messages and block anything that seems out of the ordinary. Firewalls know how hackers work and stay up to date with new hacker techniques, and keep them out of your computer.
These weren't important in the old days of dial up connections. If you were only on line for 30 minutes, you weren't much good for a hacker. They'd barely know your computer was able to be broken into before you went off line again. But for more modern systems that are on line for hours and hours, a hacker has plenty of time to break in and then take advantage of your computer.
I definitely recommend firewalls to people who use the net regularly!! Check out this easy-to-use and install FREE Firewall for your computer.