That is a very bad assumption to make. Not all AV software can detect
the various variations of it yet. In addition, there are many EU's that
will still run any executable that shows up in their inbox. Many reports
of the Microsoft Patch scam being used with this one.
Is this showing up as an issue for anyone? All I'm looking at is an MSNBC
story which gives me the impression that it's a pretty low-bandwidth deal. It
sounds like it requires intervention by the end user (or a system reboot) to
activate it, so the propagation rate ought to be very low.