Rule:
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Sid:
246

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Summary:
This event is generated when an mstream agent responds to an mstream handler's "ping" request.

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Impact:
Severe.  If the listed source IP is in your network, it may be an mstream agent.  If the listed destination IP is in your network, it may be an mstream agent.

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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.  There are "handler" hosts that are used to coordinate the attacks and "agent" hosts that launch the attack.  A handler can probe to see if an agent is active by sending it a UDP packet to destination port 10498 with a string of "ping" in the payload.  An active agent will reply with a UDP packet to destination port 6838 with a string of "pong" in payload.

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Affected Systems:
Any mstream compromised host.

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Attack Scenarios:
A mstream agent may respond with a "pong" to a "ping" request from a handler. 

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

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False Positives:
None Known.

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False Negatives:
There are other known agent-to-handler ports in addition to 6838.

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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:
NAI:
http://vil.nai.com/vil/content/v_98662.htm
SecurityFocus:
http://www.securityfocus.com/archive/82/58040
CERT:
http://www.cert.org/incident_notes/IN-2000-05.html

CVE:
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2000-0138

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