Rule:

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Sid:
448

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Summary:
This event is generated when an ICMP "Source Quench" message is generated that has a non-zero ICMP code.  

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Impact:
Informational.  This may indicate that the ICMP message has been crafted.

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Detailed Information:
An ICMP "Source Quench" message is issued by a network device that cannot handle the current volume of traffic.  The ICMP code value for this message should be 0.  If a non-zero ICMP code is observed, it may be an indication that the packet was crafted with an invalid value.

ICMP Source Quench messages may be normally sent by either a gateway or a host as a congestion control mechanism. A gateway would send them if it is running out of buffer space (needed to queue datagrams for output to the next hop) or by a host that is receiving datagrams too fast to process. Maliciously crafted ICMP Source Quench Messages may be used to force a remote host to slow down its transmission rate and causing a Denial of Service.

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Affected Systems:
This traffic should have no adverse impact.

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Attack Scenarios:
An attacker may craft an ICMP "Source Quench" message with an invalid ICMP code.  A single packet itself is not harmful, but the unusual ICMP code my indicate that this packet was abnormally generated.

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Ease of Attack:
Simple. There are many packages available to generate ICMP messages.

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False Positives:
Although rare, it is possible to observe an ICMP "Source Quench" message with a non-zero type code generated by software that does not conform to standards.

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False Negatives:
None Known.

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Corrective Action:
If a routing device in your network is generating this message, investigate why it does not have a standard ICMP code of 0.

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Contributors:
Original rule writer unknown.
Sourcefire Vulnerability Research Team
Judy Novak <judy.novak@sourcefire.com>
Additional information by Jose Hernandez <jrseal76@hotmail.com>

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Additional References:

OSVDB:
http://www.osvdb.org/15618

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