Re: bittorrent file transfer - rate limit

can you please elaborate methodology you outlined on detection of
Bittorrent encrypted connections? do you have plans to provide this
support in free IntroPro IPS software?

Thanks
Ravi

On 10/9/07, Srinivasa Addepalli <[email protected]> wrote:
>
> Hi,
>
> Older versions of Bit Torrent clients use TCP based transfer for downloading
> and uploading pieces. Later versions of clients support multiple methods for
> data transfer. Web seeding is one method which we see commonly. We also see
> Azureus client using UDP based data transfer. In addition, if peers support
> cryptography, then the connections (TCP or UDP) are encrypted.
>
> It is difficult to detect encrypted connections using typical pattern
> matching. First two packets of the connection exchange DH pairs to get
> symmetric key. This symmetric key is used to encrypt rest of stream. First
> two packets are even padded with random data of random length to avoid
> detection by any traffic enforcers. This is done very cleverly and it had
> been very successful. We believe that Traffic Heuristics combined with some
> intelligence of tracker connections is one way to detect these encrypted
> connections.
>
> By the way, IntruPro-IPS has signatures for detecting 'web seeding' and
> 'UDP' based data transfer connections in addition to TCP based connections.
> These signatures were added recently and you may like to get latest version
> of signature set.
>
> Srini
>
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On
> Behalf Of Ravi Chunduru
> Sent: Sunday, October 07, 2007 9:27 AM
> To: [email protected]
> Subject: bittorrent file transfer - rate limit
>
> i am trying to use IntroPro-IPS to limit bittorrent traffic to 20% of
> my bandwidth.
>
> it is able to detect file transfer traffic in many cases using rules
> given as part of product distribution. if i use bittorrent (downloaded
> from www.bittorrent.com) i could see that this p2p traffic is not
> exceeding 20% limit (100kbps). but if i use other client application
> such as azureus or uTorrent, i find that bittorrent data traffic is
> not recognized for some torrents.
>
> this product has facility to add new rules to detect application
> traffic. i tried to add new rules with patterns from bleedingthreats
> and l7 filters and results are same. does anybody have right patterns
> to detect all kinds of bittorrent file transfer connections?
>
> thanks
> Ravi
>
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