Rule:

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Sid:
793

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Summary:
This event is generated when an internal mail server sends an e-mail out of the network that may contain a Visual Basic Script (VBS) attachment. 

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Impact:
Malicious code infection.  This event may indicate that an internal host may be infected with some kind of malicious code.

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Detailed Information:
An outbound e-mail message that contains an attachment with a file name ending in ".vbs" may indicate that an internal host has been infected by some kind of malicious code.  A ".vbs" extension typically means that an attachment file is a Visual Basic Script.  A VBS attachment may contain executable code for a worm, virus, or trojan.

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Affected Systems:
Microsoft Windows hosts.

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Attack Scenarios:
Malicious code may be spread by e-mail containing attachments with files ending in ".vbs".

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Ease of Attack:
Simple

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False Positives:
This alert will be triggered if e-mail is sent containing a legitimate VBS attachment.

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False Negatives:
None known.

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Corrective Action:
Make sure that the suspected infected host has the most current anti-virus software.

Run a virus scan on the suspected infected host.

Configure your mail server to block attachments that contain executable code, such as those with extensions of ".vbs", ".exe", etc.

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Contributors:
Original rule writer unknown.
Documented by Steven Alexander<alexander.s@mccd.edu>
Sourcefire Research Team
Judy Novak <judy.novak@sourcefire.com>

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Additional References:

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