F-Secure has received multiple reports regarding a new trojan downloader that is being sent via email to a large number of recipients. The trojan downloader is attached to a message claiming to be a critical security update from Microsoft.
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Trojan-Download:W32/Agent.FDA arrives via email messages claiming to be a critical security update from Microsoft.The messages have an attachment named update.zip and inside the attachment there is a trojan file named update.exe. The spammed messages contain the following text:
Dear, customer New bug in Windows Kernel was found. It makes your computer vulnerable. We strongly recommend you to install this Critical Update (in attacment).Best Regards, Microsoft Window Update.
At the bottom of spammed messages there usually is a piece of random text, an attempt to bypass spam filters. Here is a screenshot of one of the spammed messages:
When extracted and run by a user, the trojan-downloader connects to a website and downloads more malicious components.