This is from the "Well, obviously" file, but as we all know, spam volume is on the rise. Everybody on the spam team knows this but we didn't really get a handle on just how much it has risen until I saw some internal statistics.
I took a look at a certain-domain-that-we-filters' total spam by volume, month to month. In February, the total amount of inbound mail that they received was around 2.5 million. In May, it was 5 million. In August, it is 9 million (and the month is only halfway finished). In 6 months, the total mail they receive has increased by 260%. However, the total mail delivered to their inboxes is only up 15%.
On an average-daily-volume basis, in February they were seeing about 85,000 total messages. Today, they are seeing close to 300,000 (about an increase in 250%). By comparison, the total marked for delivery has stayed relatively constant between 25,000 to 30,000. This means that the amount of volume has over tripled but the amount getting through is up marginally. It doesn't necessarily mean that the stuff getting through to the user is spam, however; it could just be an increase in mail traffic from their own legitimate customers.
Spammers are intensifying their attacks, but I am neither shocked by their tactics nor in awe of their resiliency. I suspect they will keep coming and keep adapting their methods, which means the cat-and-mouse game will continue.