Managing Open TCP/UDP Ports To Enhance Your Network Security

In order to surf the World Wide Web, you need some open TCP/UDP ports on your PC. HTTP Web pages use port 80, SMTP e-mail passes through port 25, and various other assigned TCP/UDP ports exist within a range from 0 . . . In order to surf the World Wide Web, you need some open TCP/UDP ports on your PC. HTTP Web pages use port 80, SMTP e-mail passes through port 25, and various other assigned TCP/UDP ports exist within a range from 0 to 65535. But what if you install a firewall and discover open TCP/UDP ports you didn't even know about?

Trojan horses, often included within Internet viruses or worms, can open additional TCP/UDP ports on your PC. The SANS Institute has created a list of Trojans and their known port use. For example, mysterious traffic on port 7597 could be a sign of the Qaz Trojan. Qaz, you might remember, opened the hole in the Microsoft Corporation that allowed a malicious user to surf their internal network in the fall of last year.

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