Rule:  

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Sid:
544

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Summary:
This event is generated when an attempt is made to retrieve a file named
"1mb" from an ftp server.

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Impact:
Possible abuse ftp behavior by hordes of warez sites, and the
existance of (potentially) illegal files/software on an ftp server.

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Detailed Information:
Warez sites have been known to name "warez" files by their size.  Large
files are split into smaller, more manageable chunks, and allow warez
sites to store large files on ftp sites in a semi-organized manner.
Once these files are uploaded, it is common practice for other warez
users to attempt to retrieve them.

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Affected Systems:
 All FTP servers

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Attack Scenarios:
As part of an attempt to store elite warez on an ftp server, an
attacker named the file "1mb" to indicate it's size.  This file is
likely part of an archive that represents a larger, most likely
illegal copy of media.

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Ease of Attack:
Simple. Exploit software is not required

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False Positives:
If a legitimate user has a legitimate file named "1mb", this rule may
generate an event.

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False Negatives:
This will detect only files named 1mb.  If a warez site decides to
start naming their files in a different way this rule will not generate
an event.

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Corrective Action:
Inspect the ftp server for a file named 1mb. If it exists, determine
if the file is legitimate, or if it was deposited by someone attempting
to use the server to distribute non-legitimate files.

Furthermore, evaluate the need for ftp write access.

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Contributors:
Original rule writer unknown
Snort documentation contributed by Jon Hart <warchild@spoofed.org>
Sourcefire Vulnerability Research Team
Nigel Houghton <nigel.houghton@sourcefire.com>

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Additional References:

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