If you had asked me what the best defense against peer-to-peer applications was a few years ago, I would have told you that the best defense was a good firewall. Obviously, firewalls are still important, but there are some peer-to-peer applications that, in most cases, are simply not affected by firewalls. Some peer-to-peer applications actually perform port scans to determine which ports are open. They then broadcast that port across the Internet so that other users of the software know how to access that machine.

Firewalls are a necessary security mechanism for any network. Just don't be naïve enough to assume that a firewall alone will protect you against peer-to-peer applications. I recommend re-evaluating your firewall's port rules from time to time to see if you can close any of the ports that are open.


Blocking peer-to-peer applications

 Home: Introduction
 Step 1: Blocking peer-to-peer applications
 Step 2: Firewalls
 Step 3: Application-level filters
 Step 4: Software restriction with Group Policy

ABOUT THE AUTHOR:
Brien M. Posey, MCSE, is a Microsoft Most Valuable Professional for his work with Windows 2000 Server and IIS. He has served as CIO for a nationwide chain of hospitals and was once in charge of IT security for Fort Knox. As a freelance technical writer, he has written for Microsoft, TechTarget, CNET, ZDNet, MSD2D, Relevant Technologies and other technology companies. You can visit his personal Web site at www.brienposey.com.
Copyright 2005 TechTarget

This was first published in July 2006

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