New spam technique?

I've been following the advice found in various threads here about reducing/spotting spam files.

As a test of what I had done, I searched for a random term to which I knew the only responses would be spam.

As well as the usual T3 hosts offering files from numerous sources with incongruous and/or uniform sizes I was surprised to find hosts using modems offering files with appropriate and varied sizes and no sources!

Has anyone else spotted this? It seems that the spammers have noted the usual advice for avoiding them (speed/size/sources) and done the complete opposite.

Sinister indeed...