We've gotten stock pumping spam for years. "Buy this penny stock, it's going to go up!". First it came as text files, then text files with random content at the bottom to avoid Bayesian filters, then images to avoid text detection, then noisy images to evade OCR.
Recently we started getting PDF stock spam. That lasted a week or two, now the new thing is ZIP stock spam. I finally opened one of the 15 ZIPs I get a day to find a 180k text file inside. 2k of stock spam text, 178k of anti-filter random text.
I first assumed all this PDF and ZIP traffic was some sort of worm traffic, an exploit payload. I'd think most users would be trained not to open strange attachments, it's suprising to me that this could be effective stock pumping spam. Maybe it's just a test.
The SEC needs to shut these operations down.