Opinion: The recent surge in spam volume is due to the assertiveness of botnets and an increase in the sophistication of their spamming efforts.
Everybody’s seen it by now. Spam is up like gangbusters in the last few months. And not just in volume; a lot more of it is getting through filtering mechanisms that had previously been pretty reliable. It’s an aggravating and depressing situation.
A number of factors have contributed to the situation, and what they all have in common, unfortunately, is that spammers are getting much more sophisticated.