Winner and new champion: Global Crossing’s AS 3549 GBLX! GBLX won the September 2012 with almost half of all the spam from the top 10 seen in the CBL data and more than a third seen from PSBL. What accounts for this surge of U.S. spammy ASNs?

Yep, it’s Festi for #1 GBLX, #2 AS 17184 ATL-CBEYOND, for #3 AS 7018 ATT-INTERNET4, #8 AS 7385 INTEGRATELECOM and #10 AS 1239 SPRINTLINK. Congratulations AT&T for making the list! Well, not really congratulations, since it means you let a lot of outbound spam out.

However, it’s Lethic for #4 AS 8047 GCI, #5 AS 22258 COMCAST-22258, and #6 AS 20115 CHARTER-NET-HKY-NC.

AS 3549 GBLX may have already peaked. AS 19529 RAZOR-PHL went up like a rocket at the end of the month! Will they swap ranks next month? And what’s driving RAZOR-PHL to the top? Hint: it’s the same as for #9 AS 25653 FORTRESSITX. Stay tuned!

-jsq