Setting up the Firewall Setting up the Firewall The next screen of the installation relates to the setup of a network firewall for your machine. A network firewall protects your computer from attacks or intrusions from malicious crackers in the network, and we’ll learn more about configuring firewalls in Chapter 12. For now, Red Hat Linux provides you with three levels of network firewall security: Highly secure firewall: This level of security is suitable for those who are quite concerned about their security. Here, all incoming network connections are disallowed unless specifically listed in the services list on the screen. To facilitate normal working, only two exceptions are made - incoming DHCP connections are allowed so that the machine can configure itself, and incoming DNS replies are allowed so that Internet applications can work normally. Medium grade secure firewall: This is the default level of security, and is generally adequate while using the Internet. This level disallows incoming network connections to privileged ports like web, SMTP mail, etc. However, you can customize this level to allow certain incoming connections to services that your desktop is providing. For example, if you set up a web server on your machine and want others to access it, you can check the WWW option in the services list on the screen. No firewall: If you are unlikely to connect to the Internet, or if you are not concerned with cracking activities that can be directed by troublesome individuals on the Internet or your LAN, then you can select this option. This option doesn’t set up any firewall on your machine. In other words, it allows any outside individuals to access network resources on your computer. Note Selecting the No firewall option doesn’t necessarily mean that all users on the network have direct and unchecked access to your computer’s network resources. A firewall is just the first line of defense against intruders. Most network applications have some form of access control that decides who finally gets to use these resources. 28
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