Rule:

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Sid:
250

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Summary:
The event is generated when a DDoS mstream handler responds to an mstream client.

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Impact:
Severe.  If the source IP is in your network, it is possibly an mstream handler.  If the destination IP is in your network, it is possibly an mstream client.

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Detailed Information:
The mstream DDoS uses a tiered structure of compromised hosts to coordinate and participate in a distributed denial of service attack. At the highest level, clients communicate with handlers to direct them to launch attacks.  A client may contact a handler using a TCP SYN packet to destination port 15104.  A listening handler would respond to this on source port 15104 with a string of ">" in the payload.

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Affected Systems:
Any mstream compromised host.

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Attack Scenarios:
After a host becomes an mstream handler, the client will attempt to communicate with the handler.  A handler will respond to this communication.


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Ease of Attack:
Simple. mstream code is freely available.

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False Positives:
A legitimate server port of 15104 will cause this rule to fire.  This rule may also generate a false positive if port 15104 is selected as an FTP data port.

Use of Gnutella will also cause this rule to generate an event, the gnutella protocol makes extensive use of XML if the port in use is 15104 this rule will generate a large number of events.

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False Negatives:
There are other known client-to-handler ports in addition to 15104.

Corrective Action:
Perform proper forensic analysis on the suspected compromised host to discover the means of compromise.

Rebuild a confirmed compromised host.

Use a packet-filtering firewall to block inappropriate traffic to the network to prevent hosts from being compromised.

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Contributors:
Original rule writer unknown
Sourcefire Research Team
Judy Novak <judy.novak@sourcefire.com>

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Additional References:


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