Always use a hardware-based or software-based firewall on computers connected to the Internet. Ubuntu includes a graphical firewall configuration client named gnome-iokkit, along with a console-based firewall client named lokkit. Use these tools to implement selective or restrictive policies regarding access to your computer or LAN.
Start the lokkit command from a console or terminal window. You must run this command as root; otherwise, you will see an error message like this:
ERROR - You must be root to run lokkit.
Use the sudo command to run lokkit like this: $ sudo "/usr/sbin/lokkit"
After you press Enter, you see a dialog as shown in Figure 31.1. Press the Tab key to navigate to enable or disable firewalling. You can also customize your firewall settings to allow specific protocols access through a port and to designate an Ethernet interface for firewalling if multiple NICs are installed. Note that you can also use a graphical interface version of lokkit by running the gnome-lokkit client during an X session.
Figure 31.1. Ubuntu's lokkit command quickly generates firewall rules in memory for Linux.
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A firewall protects against unauthorised network intrusions. High security blocks oil incoimng accesses, Wediurr, blocks access to system services (such as telnet Or printing), but allows Dther connections. Ho firewall allows all connections and is not recomwnded.
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