As an alternative to hardware router security setups, you can use software firewalls designed for the home office. Software firewalls track incoming and outgoing Internet connections and traffic by port number, which is no small task: Tens of thousands of ports are available for inbound and outbound communications. When a machine receives a connection request from outside your network, a software firewall consults rules that you define to determine whether to permit the connection. The same process occurs for outbound connections from within your home network.
When evaluating software firewalls, you need to select a software-based firewall that lets you
- run the software in learn mode (learn mode monitors the use of selected applications and automatically creates "sandboxes" that allow applications to access only those resources required by normal operation; this automatic process is important because manually configuring your firewall to behave properly with your applications can be a chore)
- easily evaluate an intrusion
- define custom rules.
To learn about software firewall products for the home office, check out the Firewall Guide Software Reviews Web site at http://www.firewallguide.com/software.htm. This site presents up-to-date descriptions of each product, recent technical evaluations, and links to vendor Web sites that provide evaluation software you can download. Most software firewall vendors let you download and run their products for home evaluation at no charge or for a small fee.
Although software firewalls provide more control and power than hardware routers, you need to consider several factors before you decide to use a software-based firewall solution. Most important, the hardware-based solutions I describe in this article are usually easier to install and configure. After you set up a cable or DSL router, you never have to touch it again. You don't have to worry about maintenance schedules or procedures. Also, the cable or DSL router provides fault tolerance. If the device's power source fails and the router becomes inoperable, you'll lose your Internet connection anyway¾you won't be vulnerable to attack because of this one point of failure.
A software firewall is simply a program that runs on a computer—preferably a machine that you dedicate to the purpose. If you run a software firewall on a machine that you use for other tasks, you expose the firewall to the various weaknesses of the machine's OS and the problems that the machine's users might introduce. For example, a user might inadvertently terminate a software firewall, thereby exposing your home network to attack. Software firewall capabilities are usually superior to those of the router-based hardware equivalents I've discussed, but the software solution requires much more time to configure, diagnose, and maintain them.