Remarkably, it seems that 70% of the world’s spam emails were originating from an American firm called McColo. On November 11th, two American internet service providers cut them off from the web, leading to the huge drop in the global volume of spam. It is estimated that 90% of spam messages are actually sent by computers that have been compromised by viruses, which makes it a bit surprising that such a drop could be generated by disconnecting one firm. Clearly, it is a network that needed central direction to operate. Those that emerge as successors will probably be more robust, located in more unpoliced jurisdictions, or both.
While the respite is likely to be temporary, the situation may reveal some useful information on the practice and economics of spam. This unrelated paper (PDF) examines the latter. The researchers infiltrated a segment of the Storm Botnet and monitored its activity and performance. On the basis of what they observed and estimates of the rest, they concluded that the botnet earned about 3.5 million dollars a year by selling pharmaceuticals. While that isn’t an inconsiderable sum, I suspect it is less than is being spent by companies combatting the flood of spam messages themselves.