Certain network tools can be misused by crackers to break into a computer or just cause it problems. In the past, the traceroute and ping tools, among others, have been used to launch denial-of-service (DoS) attacks against computers.
Ubuntu is set to allow these tools to operate by default. If you want to adopt a belts-and-suspenders approach to your computer's security, you can opt to disable them. If you don't know what ping and traceroute are, you're clearly not going to miss them, so there will be no harm in disallowing them. Here's how:
1. In the Firestarter main window, click Edit > Preferences.
2. On the left side of the Preferences window, click ICMP Filtering. Then click the Enable ICMP Filtering check box, as shown in Figure 9-21. Don't put a check in any of the boxes underneath, unless you specifically want to permit one of the services.
3. Click the Accept button to finish.
There's a fine line between security and paranoia. Using Firestarter gives you the opportunity to ensure your system is secure, without needing to constantly reassess your system for threats and live in fear.
When considering your system security, remember that most burglars don't enter a house through the front door. Most take advantage of an open window or poor security elsewhere in the house. In other words, when configuring your system's security, you should always select every option and extra layer of security, even if it might not appear to be useful. You should lock every door and close every window, even if you don't think an attacker would ever use them.
Provided a security setting doesn't impact your ordinary use of the computer, you should select it. For example, deactivating the ping response of your computer might sound like a paranoid action, but it's useful on several levels. First, it means your computer is less easy to detect when it's online. Second, and equally important, it means that if there's ever a security flaw in the ping tool (or any software connected with it), you'll be automatically protected.
This illustrates how you must think when configuring your system's security. Try to imagine every situation that might arise. Remember that you can never take too many precautions!
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