A firewall is software or hardware that helps guard your computer against hacker attacks, and against some computer viruses and worms that try to reach your computer when it is connected to the Internet. A firewall acts like a gatekeeper—it lets in computer connections and data from sources you trust, and it keeps out the ones you don’t.
Windows Live OneCare Firewall works like a gate in two directions. Not only does it help keep bad things from getting in, but it also helps to keep malicious programs that might have slipped onto your computer from sending your personal data out.
If your computer is not protected when you connect to the Internet, hackers can gain access to the personal information stored on it. They can install code on your computer that destroys files or causes malfunctions. They can also use your computer to cause problems on other home and business computers connected to the Internet. A firewall helps to screen out many kinds of malicious Internet traffic before it reaches your system.
Some firewalls (such as Windows Live OneCare Firewall) can also help prevent others from using your computer to attack other computers without your knowledge. Using a firewall is important no matter how you connect to the Internet—dial-up modem, cable modem, or digital subscriber line (DSL or ADSL).
The Firewall helps protect your computer from two kinds of unauthorized connection attempts:
The Firewall checks any program, computer, or service that tries to create a connection to your computer from the Internet, and by default, blocks them. You can choose to enable certain limited connectivity to your computer by changing some of the advanced settings in Windows Live OneCare Firewall. See Related Topics for more details.
The Firewall checks programs when they first try to connect to the Internet from your computer. If a program is not recognized by the Firewall policy (A list of recognized programs that the Firewall uses to decide which programs have automatic access to the Internet. The Firewall policy is updated periodically as part of the automatic process of updating Windows Live OneCare. ) , Firewall blocks the program by default, and then shows you a dialog box asking you if you want to continue blocking the program. Blocked programs are not allowed to create connections from your computer to the Internet. This is important because some malicious programs, called Trojan horses (A program that masquerades as another common program in an attempt to receive information. An example of a Trojan horse is a program that behaves like a computer logon screen to retrieve user names and password information that the writers of the Trojan horse can later use to break into the system.) , can gather your personal information and try to send it out. Windows Live OneCare Firewall helps prevent that.
The Windows XP operating system comes with a built-in firewall called Windows Firewall. Basically, Windows Firewall works in a similar way to Windows Live OneCare Firewall, but Windows Firewall only checks for programs that are trying to connect to your computer from the Internet and does not check programs that are already on your computer and are trying to create a connection out.
Because two firewalls should not be turned on at the same time, Windows Live OneCare turns off Windows Firewall if the latter is running. This does not reduce your computer’s security.