Rule:

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Sid:
273

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Summary:
This event is generated when a remote attacker transmits fragmented IGMP packets with malformed headers to the internal network, indicating an IGMP Denial of Service (DoS) attack.

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Impact:
Denial of service.

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Detailed Information:
If an IGMP packet with a malformed header is transmitted to an unpatched Microsoft Windows computer, the computer may crash when it attempts to process the packet.  

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Affected Systems:
Microsoft Windows 95
Microsoft Windows 98
Microsoft Windows 98 SE
Microsoft Windows NT 4

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Attack Scenarios:
An attacker sends fragmented IGMP packets with malformed headers to a target computer. If the computer is running an unpatched version of Windows, it may crash.

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Ease of Attack:
Simple. Exploits exist.

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False Positives:
None known.

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False Negatives:
None known.

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Corrective Action:
Install the latest patches available for your operating system. See http://www.microsoft.com/technet/security/bulletin/ms99-034.asp for more information.

Implement a packet-filtering firewall to block inappropriate traffic to the network.

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Contributors:
Original rule writer unknown
Sourcefire Research Team
Sourcefire Technical Publications Team
Jen Harvey <jennifer.harvey@sourcefire.com>

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Additional References:

Bugtraq
http://www.securityfocus.com/bid/514

Microsoft
http://www.microsoft.com/technet/security/bulletin/ms99-034.asp

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