Rule:

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Sid:
613

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Summary:
This event is generated when a scan is detected. 

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Impact:
Information gathering.

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Detailed Information:
This event indicates that an attempt has been made to scan a host.

This may be the prelude to an attack. Scanners are used to ascertain 
which ports a host may be listening on, whether or not the ports are 
filtered by a firewall and if the host is vulnerable to a particular 
exploit.

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Affected Systems:
Any host.

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Attack Scenarios:
An attacker can determine if ports 21 and 20 are being used for FTP. 
Then the attacker might find out that the FTP service is vulnerable to a
particular attack and is then able to compromise the host.

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Ease of Attack:
Simple.

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False Positives:
A scanner may be used in a security audit.

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False Negatives:
None Known.

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Corrective Action:
Determine whether or not the scan was legitimate then look for other 
events concerning the attacking IP address.

Check the host for signs of compromise.

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Contributors:
Sourcefire Research Team
Brian Caswell <bmc@sourcefire.com>
Nigel Houghton <nigel.houghton@sourcefire.com>

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Additional References:


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