A long time ago I started tracking spam from the big 4 web mail services – AOL, Yahoo, Google and Microsoft (Hotmail). The trends didn’t change very often and it was usually pretty consistent over the time frames that I observed: AOL was the cleanest, Yahoo and Hotmail tended to flip flop amongst themselves.
Well, I finally decided to have another look at spam from these services and things have changed quite a bit since June. Google (mail from IPs listed in Gmail’s SPF record) is now the one that sends us the most spam by far. In fact, in June we saw a sudden, dramatic increase in spam from them. I am not sure if something changed in our collection and analysis scripts (unlikely since I haven’t changed anything) or if spammers made a decided shift into Google (more likely).
Observe that Hotmail had some serious problems back in Feb-April of this year but got a lot better after that. They seem to be edging up a bit which appears to coincide with a slight decrease in spam from Google. This suggests a slight shift from Google to Hotmail.
Yahoo remains relatively consistent although the spike in Gmail appears to be coincided with a small decrease in Yahoo. If my interpretations are correct, then spam from Gmail has gotten suddenly worse for them (about 4x worse) over the past 3 months and doesn’t seem to be getting much better.