Rule:
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Sid:
228

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Summary:
This event is generated when a Tribe Flood Network (TFN) Distributed Denial of Service (DDoS) client communicates with the TFN handler daemon to spawn a shell.

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Impact:
Attempted DDoS.  If the listed source IP is in your network, it may be a TFN client.  If the listed destination IP is in your network, it may be a TFN handler daemon.

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Detailed Information:
The TFN DDoS uses a tiered structure of compromised hosts to coordinate and participate in a distributed denial of service attack. Clients communicate with daemons to direct them to launch attacks. A client will communicate with a daemon to spawn a shell via an ICMP echo reply with an ICMP identification number of 456 and an ICMP sequence number of 0.  

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Affected Systems:
Any TFN compromised host.

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Attack Scenarios:
After a host becomes a TFN client, it will attempt to communicate with other TFN handler daemons.

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

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False Positives:
It is possible that this is a legitimate echo reply to a previous echo request that had an ICMP identification value of 456 and an ICMP sequence number of 0.  

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False Negatives:
None Known.

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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 written by Max Vision <vision@whitehats.com>
Sourcefire Research Team
Judy Novak <judy.novak@sourcefire.com>

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Additional References:

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

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