Rule:

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Sid:
270

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Summary:
This event is generated when an attempt is made to issue a Teardrop Denial of Service (DoS) attack.

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Impact:
Denial of Service.

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Detailed Information:
Teardrop exploits a vulnerability in some TCP/IP stack implementations.

The program sends a specially crafted fragmented packet where the first fragment has offset 0 and data length N and the second fragment has an offset less than N (The fragments overlap).  The resulting packet cannot be properly assembled.

Systems may hang or crash.

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Affected Systems:
	Windows 95
	Windows NT 4.0 SP3 and earlier
	HP HPUX 10.34 and earlier
	Linux kernels 2.0.31 and earlier
	FreeBSD 3.0 prior to October 27, 1998

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Attack Scenarios:
The can be done remotely against any open UDP port using a spoofed address.

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Ease of Attack:
Simple. Tools are readily available and require little knowledge on the part of the attacker.

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False Positives:
None known.

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False Negatives:
None known.

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Corrective Action:
Patches are available from all affected vendors.  Newer versions from each vendor are not vulnerable.

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Contributors:
Original Rule Writer Unknown
Sourcefire Research Team
Nigel Houghton <nigel.houghton@sourcefire.com>
Snort documentation contributed by Steven Alexander<alexanders@mccd.edu>

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Additional References:

FreeBSD:
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/old/FreeBSD-SA-98:08.fragment.asc

OSVDB:
http://www.osvdb.org/5727

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