So the media is abuzz with news of the takedown of the Grum botnet, which has caused a big reduction in spam. Make no mistake this is welcome news indeed, and credit to Atif Mushtaq from FireEye for taking action. However, there are also some other things going on here which are impacting on spam output.
It's important to see this week's changes in light of the overall long term spam trend, which continues to go down, down, down. You can get a glimpse of the scale of the change by looking at our Spam Volume Index below. As I stated in a blog last week there are a number of reasons for this huge decline, including spam affiliate programs closing (Spamit.com), botnets disabled (Rustock), botnet operators apprehended (Mega-D), infighting between spamming rivals and other botnets going strangely quiet (Festi). The big drop in September/October 2010 was Spamit.com closing.
In the last two weeks we have seen spam output from Lethic drop to nothing, as well as Donbot going quiet. Lethic was formerly the largest spammer, so this is very significant. And on top of that, we have the Grum control server takedown this week, which has caused output from Grum to slow to a dribble. You can see this effect in the Spam by Spambot chart attached. (Note the spambot stats are driven off a sample, so the absolute numbers in themselves do not mean much, it is the trend and scale of change is important.)
So over the last month we have seen the total number of spam hitting our servers cut in half, which coincides with what others are seeing. The output from Grum that is hitting our servers has declined to a dribble, a mere 5% of what it previously was. This suggests that at least one control server is active somewhere.
The interesting thing is that output from Lethic and Donbot spam started declining prior to attempts to takedown Grum servers, and we still don't know why. Maybe they are all partying together in the Greek Islands.
Finally, while these drops in spam are very welcome, history has shown us that the botnet operators can recover, relocate their servers and build their bot armies again. It would not surprise me to see Grum, Lethic, and some of the others resurrect themselves again in short order.