
Rule:  

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Sid:
796

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Summary:
This rule has been placed in deleted.rules. It has been superceded by
sid 721.

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Impact:
Mail worms may spread rapidly because users execute them.

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Detailed Information:
Windows systems are often configured not to display file extensions.
By adding a second extension, users get confused and think that an
executable is an EXCEL spreadsheet - e.g. businnesplan.xls.vbs gets displayed as
businessplan.xls but is a visual basic script and not an EXCEL spreadsheet.

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Affected Systems:
 
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Attack Scenarios:
Famous worms (ILOVEYOU, KOURNIKOVA) are based on this method. Warning:
An EXCEL spreadsheet is in now way more secure than a visual basic script.
Wrongly configured antivirus software my ignore this files and
let a macro virus pass.

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Ease of Attack:
Very easy. One needs to attach a file and hope that it gets executed.

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False Positives:
None Known
Could be an error on sender's side.

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False Negatives:
None Known
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Corrective Action:
Use antivirus software. Configure mail clients securely, especially when
using windows desktops. Educate your mail users. Deny all attachments at
the gateway if you can.

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Contributors:
Original rule writer unknown
Snort documentation contributed by tobias.haecker@to.com
Sourcefire Vulnerability Research Team
Nigel Houghton <nigel.houghton@sourcefire.com>

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Additional References:
See websites of antivirus companies.

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