Rule:

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Sid:

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Summary:
This rule detects certain phishing attempts sent via Microsoft Messenger.

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Impact:
Users who are fooled by the phising attempt may be tricked into downloading 
malicious code.

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Detailed Information:
The Microsoft Messenger service, which is enabled by default on many Windows 
systems, allows remote users to send pop-up messages to a given system. While 
legitimate uses exist, many of these pop-ups contain adware, spyware, and/or 
phishing attempts. This rule detects a common phishing attempt, which "warns" 
users that their registry is corrupted and directs them to download software to 
fix the "problem" at a malicious web site.

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Affected Systems:
Any Windows system with Microsoft Messenger enabled and reachable from the 
Internet.

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Attack Scenarios:
Attackers will typically use publicly available scripts to send malicious 
messages.

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Ease of Attack:
Simple; public scripts exist for sending malicious messages.

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False Positives:
None known.

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False Negatives:
None known.

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Corrective Action:
Block Microsoft Messenger at your firewall and/or disable it on individual 
machines, and educate your users regarding the dangers of following links in 
such messages.

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Contributors:
Sourcefire Vulnerability Research Team
Sago Networks
Dan Protich <dprotich@sagonet.com>

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Additional References:

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