From [H]ard|OCP:
I had three 250GB arrays blow out last night
when this first hit . Be very careful.
Heavyweight operates much like other self-replicating, self-spreading viruses with one weighty exception, it arrives as a compressed attachment. What is unique about this compressed file, such as zip or tar files, is the density of compression. The file is so densely packed that the attachments weighs 1,000,000 times more than normal compressed data.