5 or 6 emails have come in today with 0-byte .VBS file attachments, all with different names (the_message.vbs, toy.vbs, info.vbs, etc.)

I'm not particularly concerned about it as we block all executable attachments anyway, plus all our external mail gets routed through MessageLabs, but I wonder if it's a new worm that escape prematurely?

The message body just contains:
The message subjects are pretty much random too.

Any other mail administrators seen this coming up today?