Windows XP Hacks

Close Down Open Ports and Block Protocols

You don’t need a firewall to protect your PC; you can manually close down ports and block certain protocols.

As noted in [Hack #46] and [Hack #48], firewalls can protect your PC and your network from intruders. But if you don’t want to install a firewall and you still want protection, you can manually close down ports and block protocols.

Some of these ports and protocols are more dangerous than others. For example, leaving open the port commonly used by Telnet (port 23) means that someone could use that service to take control of your PC. And the infamous Back Orifice Trojan, which also can give malicious users complete control of your PC, uses a variety of ports, including 31337 and 31338 among others. For a list of which ports are used by Trojans, go to http://www.sans.org/resources/idfaq/oddports.php.

In this hack, you’ll need to know which ports you want to be open on your PC, such as port 80 for web browsing, and you’ll close down all others. For a list of common ports, see Table 5-2 [Hack #49]. For a complete list of ports, go to http://www.iana.org/assignments/port-numbers.

To close down ports and protocols manually, right-click on My Network Places and choose Properties to open the Network Connections folder. Right-click on the connection for which you want to close ports and choose Properties. Highlight the Internet Protocol (TCP/IP) listing and choose Properties. On the General tab, click the Advanced button. From the Advanced ...