INFO-SEC: Alert – New Mass Mailer Worm Affecting Some Exchange Customers

#Exchange #Exchange2010

Received this from a number of different people today (Thanks Mitch!)

Emerging Malware Issue: Visal.B:

Worm:Win32/Visal.B is a new worm, written in Visual Basic, that is currently propagating in part using social-engineering. We strongly encourage customers to be cautious about clicking suspicious or even simply unexpected links in email, even if it’s sent by someone you know. Getting infected by Visal.B is an example of what happens if you aren’t careful.

The threat has a timestamp of 9/3/2010 and spreads using two techniques: mass emailing, and copying itself to local drives (C: and H:) and network shares. The threat will copy itself to various drives on the local system along with an autorun.inf file, and will also send itself to all contacts that it can find on the compromised system via email.

Visal.B uses MAPI to perform a mass mailing to all contacts that it finds on the compromised system. In a corporate environment the “address book” may be extensive. As more machines on a corporate network are infected, more and more email is sent around on the local network, which can cause mail server performance degradation. The threat also sends back information about the compromised system, specifically IP addresses and system information via a built-in SMTP/ESMTP (mail-transfer) engine.

Microsoft Malware Protection Center Technical Summary:

Microsoft Malware Protection Center Latest Definitions:

Microsoft Malware Protection Center Blog Post:

Microsoft TechNet Wiki on Visal-b:

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