Rule: 

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Sid: 
547

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Summary: 
This event is generated when an attempt is made to create a directory name that begins with a period on an FTP server.

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Impact: 
Unauthorized file storage.  An attacker may attempt to create a directory name that begins with a period on an FTP server, possibly in preparation to store unauthorized files.


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Detailed Information: 
An attacker may attempt to create a hidden directory name that begins with a period on an FTP server .  This hidden directory is hard to discover, permitting attackers to store unauthorized "warez" files, such as unlicensed or pirated software.

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Affected Systems: 
FTP servers

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Attack Scenarios: 
An attacker may attempt to create a hidden directory name that begins with a period to store unauthorized files.

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Ease of Attack: 
Simple

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False Positives:
It is remotely possible that an authorized directory exists with a name that begins with a period.

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False Negatives: 
Hidden directories other than those with a name that begins with a period may be created to store "warez" files.

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Corrective Action: 
Assign restrictive permissions to all directories so unauthorized users cannot navigate or write to them.

Regularly monitor directories for sudden or drastic increased use of space.

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Contributors: 
Original rule writer unknown
Modified by Brian Caswell <bmc@sourcefire.com>
Snort documentation contributed by Chaos <c@aufbix.org>
Sourcefire Research Team
Judy Novak <judy.novak@sourcefire.com>

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Additional References:

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