'Microsoft Support' has something very important to say(F-Secure : News from the Lab:)

support@microsoft.comからのウイルスが出ているそうです。

A few hours ago we have received reports of an important update supposedly coming from Microsoft Support. Since this 'update' is not part of the monthly cycle, we were of course suspicious.

Looking at the email, our suspicions grew due to the glaring typos and the non-Microsoft domain link.

Backdoor:W32/VanBot.CAで検知するそうですが、、、Trendはまだだろうなぁ

Good thing, the sample contained in the link is now detected as Backdoor:W32/VanBot.CA since 2007-05-28_05.
Updates are always good, but in this case, keep your virus definitions updated instead.