The sky is falling! The sky is falling! Spam has doubled / spammers are winning / spam is 80% of all mail / 90% of mail / 110%, etc. etc. etc...
Here's my take on what's happening. A bit stream-of-consciousness, so please excuse. Grateful for your thoughts.
The growth in spam is chiefly down to two factors:
- Demand-side -- stock kiting gangs wanting access to more and more sending capacity
- Supply side -- new, bigger botnets with more sophisticated command and control mechanisms, which are more resistant to being shut down and can send fewer messages per zombie (because they're bigger), so stay under the radar longer
- New botnets spewing spam from PCs not on blacklists, so a smaller proportion of spam gets rejected (and thus never seen in quarantines)
- New botnets resistant to anti-spam techniques such as greylisting (because they have real, autonomous MTAs), so a smaller proportion of spam gets rejected (and thus never seen in quarantines)
- New botnets employing content morphing tricks that are fooling many vendors' content filters, so more spam reaches the inbox -- then naive commentators wrongly assume that a doubling of spam in the inbox equals a doubling of spam on the Internet
Some anti-spam vendors are coping quite adequately with the new techniques, but seem to have broken PR departments ;-)
I trust Commtouch's and MessageLabs's data more than most -- my reading is that spam volumes increased measurably about a month ago, but not to the extent that Chicken Licken would have us believe.