Rule: 

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Sid: 
100000160

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Summary: 
This event is generated when an abnormally larger number of packets are 
received from a single source by an SIP-enabled host in a short period of time.

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Impact:
This can be an indication of a denial of service attack in progress.

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Detailed Information:
This rule is designed to detect overly large amounts of traffic coming from a 
single host to the SIP port on an internal host, as it is possible to cause a 
denial of service by sending a large number of packets with invalid data.

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Affected Systems:
Any which implement the SIP protocol.

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Attack Scenarios:
An attacker could use a script to flood a system with invalid messages, causing 
a denial of service.

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Ease of Attack:
Simple, as it is trivial to write a script to generate random data.

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False Positives:
Known SIP proxies may receive a high volume of legitimate data, and NAT devices 
may appear to be sending a larger amount of data than a regular host. It is 
recommended that users whitelist known SIP proxies and NAT devices.

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False Negatives:
None known.

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Corrective Action:
Use a firewall or other access-restriction device to block unwanted messages at 
your network's border.

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Contributors:
Jiri Markl <jiri.markl@nextsoft.cz>
Sourcefire Research Team

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Additional References
Other:

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