New attachment type?

[mailscanner at barendse.to]

Hello list

Just received a new virus mail where the body of the text is asking to 
"update" IMAP adress blabla

There is a 159 byte attachment with the email named "open" without any 
extension at the end. Outlook does seem to recognize it as there it places 
an icon before the attachment (windows logo at the top with a rectangle 
at the bottom).

Is anyone else seeing this, how can I stop it or how can I block 
attachments without extension?

Thanks!!
Remco