Today someone has taken the original Mydoom.A worm, unpacked the UPX packing and repacked it with Petite - and distributed the end result.

End result: a worm which is functionally identical to original Mydoom but which might be missed by some antivirus programs. We don't...F-Secure actually detects this as Mydoom.A by default.

Some other antivirus programs might detect it as Mydoom.D.