Still so big

I’m still receiving over 2000 SoBig-generated junk messages per
day.  The annoying part are the bounces from emails that spoof my
return address.  A few dozen of those per day go through my
current spam filters.  I’m just worried about what things will be
like when the next, even more virulent version of the worm comes
out.  I may be forced to go to challenge/response.