Rule:  

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Sid:

2180

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Summary:

This event is generated when a BitTorrent client connects to a tracker 
to gain access to a BitTorrent network.  

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Impact:

Possible violation of policy and abuse of network resources.

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Detailed Information:
BitTorrent is a peer-to-peer application used for simultaneous downloads
of large files.  BitTorrent is designed to allow multiple peers to 
download large files simultaneously without using extraneous bandwidth 
from a centralized server.

BitTorrent's centralized server, called a tracker, refers peers to each 
other. This rule looks for a request sent to a BitTorrent tracker from a
peer.

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Attack Scenarios:

A user downloaded a BitTorrent client and attempts to download files 
from a BitTorrent network.

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Ease of Attack:

Unix, Windows, and MacOS clients are publicly available for BitTorrent.

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False Positives:

Other web-based applications could use similar URLs and parameters.

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False Negatives:

The URL path "/announce" is hardcoded in the BitTorrent tracker.  If the
URL was changed in the tracker, then this rule would not generate an 
event.

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Corrective Action:

If this is a violation of network policy, take appropriate steps to 
prevent further violations.

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Contributors:

Sourcefire Research Team
Brian Caswell <bmc@sourcefire.com>

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Additional References:

Bittorrent Protocol Specification
http://bitconjurer.org/BitTorrent/protocol.html

Wikipedia
http://en.wikipedia.org/wiki/BitTorrent

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