How Effective is P2P Blocking?

This past week, a discussion about peer-to-peer (P2P) blocking tools came up in a user group that I follow. In the course of the discussion, different IT administrators chimed in, citing their favorite tools for blocking P2P traffic.

At some point in the discussion, somebody posed the question, “How do you know your peer-to-peer tool is being effective?” For the next several hours the room went eerily silent.

The reason why this question was so intriguing to me is that for years I collaborated with various developers on creating an open-source P2P blocking tool using layer 7 technology (the Application Layer of the OSI Model). During this time period, we released several iterations of our technology as freeware. Our testing and trials showed some successes, but we also learned how fragile the technology was and we were reluctant to push it out commercially. I had always wondered if other privately-distributed layer 7 blocking tools had found some magic key to perfection?

Sometimes, written words can be taken as fact even though the same spoken words might be dismissed as gossip; and so it was with our published open source technology. We started getting indications that it was getting picked up and integrated in other solutions and touted as gospel.

Our experience with P2P blocking:

Our free P2P blocking tool worked most of the time – maybe eighty percent. Eighty percent accuracy is fine for an experimental open-source tool. Intuitively, a blocking tool is expected to be 99.9 percent effective. Even though most customers would likely not conclusively measure our accuracy, eighty percent was too low to ethically sell this technology without disclosures.

The on-line discussion ended fairly quickly when the question of accuracy was brought up, and I think it is safe to assume the silence is an indication that nobody else was achieving better than eighty percent.

How do you validate the effectiveness of a P2P tool?

1) Brute force testing:

I am not aware of too many IT administrators that have the time to load up six or seven different P2P clients on their laptops, and download bootlegged Madonna videos all day.

In testing P2P clients, we infected several computers with just about every virus in circulation. Over time, you can get a rough idea of how deep you must go to expose weaknesses in your tool set. To be thorough, you can’t stop at the first P2P client tool. In the real world, users on your network will likely search for multiple P2P clients, especially if the first one fails. Once they find a kink in the armor, they will yap to others, exposing your Achilles heel.

2) Reduction of RIAA requests:

Most small-to-medium ISP’s don’t really think about P2P unless they get RIAA requests or their network is saturated.

RIAA requests seem to be a big motivator in purchasing technology to block P2P. If you are getting RIAA requests (these are letters from lawyers threatening to sue you for copyright infringement), you can install your P2P blocking tool, and if in the next week your notifications of copyright violations are way down, you can assume that you have put a good dent in your P2P downloading issue.

3) Reduced congestion:

Plug your P2P tool in and see if your network utilization drops.

4) Lower connection rates through your router:

One of the signatures of P2P is that clients will open up hundreds of connections per minute to P2P servers in order to download content. There are ways to measure and quantify these connection rates empirically.

Other observations:

Many times we’ll hear from an ISP/operator claiming they have P2P users run amok on their network, however analysis often shows most of their traffic is video – Netflix, YouTube, Hulu, etc.

Total P2P traffic has really dropped off quite a bit in the last three or four years. We attribute this decline to:

1) Legal iTunes. 99 cent songs have eliminated the need for pirated music.

2) RIAA enforcement and education of copyright laws.

3) The invention of the iPad and iPhone. These devices control the applications which run on them (they are not going to distribute P2P clients as readily).

One method to handle P2P problems is to control all the computers in your environment, scan them before granting network access, and then block access to P2P sites (the sites where the client utilities are loaded from).

Note: once a P2P client is loaded on a computer you cannot block any single remote site, as the essence of P2P is that the content is not centralized.


Results of different P2P blocking techniques are often temporary, especially when you have an aggressive user base with motivation to download free content.

3 Responses to “How Effective is P2P Blocking?”

  1. Steve Bohrer Says:

    The past few years have shown a rise of “http” file sharing sites, which I think has contributed to the decline of P2P traffic. However, the HEOA seems to specifically require that we (a small college) take action to limit “P2P” sharing. Thus, I need to target P2P, even if there is an order of magnitude more stuff coming in via other paths.

    Bottom line, of course, is that most users are happier most of the time when we limit the bandwidth hogs, no matter which protocols the hogs are using.

  2. NetEqualizer News: October 2011 « NetEqualizer News Blog Says:

    […] Posts How Effective is P2P Blocking?Nine Tips And Tricks To Speed Up Your Internet ConnectionDynamic Reporting With The NetEqualizerWhat […]

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