Rule:

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Sid: 1640

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Summary:
This event is generated when activity relating to network chat clients is detected.

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Impact:
Policy Violation. Use of chat clients to communicate with unkown external sources may be against the policy of many organizations.

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Detailed Information:
Instant Messaging (IM) and other chat related client software can allow users to transfer files directly between hosts. This can allow malicious users to circumvent the protection offered by a network firewall.

Vulnerabilities in these clients may also allow remote attackers to gain unauthorized access to a host.

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Attack Scenarios:
A user may transfer sensitive company information to an external party using the file transfer capabilities of an IM client.

An attacker might utilize a vulnerability in an IM client to gain access to a host, then upload a Trojan Horse program to gain control of that host.

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Ease of Attack:
Simple.

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False Positives:
None Known

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False Negatives:
None Known

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Corrective Action:
Disallow the use of IM clients on the protected network and enforce or implement an organization wide policy on the use of IM clients.

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Contributors:
Sourcefire Research Team
Brian Caswell <brian.caswell@sourcefire.com>
Nigel Houghton <nigel.houghton@sourcefire.com>

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Additional References:
IRC Protocol
http://www.irchelp.org/irchelp/rfc/

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