In the fd.o mime database there are two seperate definitions for ASF and WMF:

Microsoft ASF video (*.asf, *.asx)
Microsoft WMV video (*.wmv)

However, I often encounter ASF files that carry the *.wmv file extension. In
Gnome, this means that the file magic says it is a Microsoft ASF Video (which
would appear to be indeed so) but it gives a warning stating that the file
proclaims to be a Microsoft WMV video instead of ASF (due to the file extension)
and Gnome refuses to open the file because it might be a "virus" or something bad.

Renaming the file to *.asf works, and the file opens properly. I first thought
that someone misslabeled the ASF file with a *.wmv file extension, but since
then I have found about ten to fifteen ASF files from different sources that
carry the *.wmv extension.

A nice example of such an ASF file is linked in this TheRegister article:
http://www.theregister.co.uk/2004/07/06/sourcenext_horse/

Should *.wmv be considered an extension for Microsoft ASF Video as well? Or is
Gnome wrong in stating that there might be a "security risk" in opening an ASF
file with a *.wmv file extension?