Hackers often use available ports to get into a system, frequently preceding an intrusion with a port scan that looks for any open ports at a given IP address. Think of a burglar rattling all the doorknobs on your block to see if any house is open. Ports are opened or closed, but by default they are supposed to respond to any request regardless of their state. Most firewall software prevents your ports from responding to incoming requests at all. When ports ignore incoming traffic, it's impossible for intruders to know whether a PC is connected to that IP address.
Most firewalls distinguish between inbound and outbound traffic.
Once installed, a Trojan can monitor your keystrokes and send logs back to a hacker. Eventually, some of these keystrokes might contain sensitive information. By blocking outbound traffic on unused ports, you reduce the odds of a Trojan compromising your machine's security. We cannot promise to adopt every suggestion, or to answer each and every e-mail. We DO promise, however, to read all your suggestions.