83% of all spam originates from botnet controlled computers according to a recent report from MessageLabs.
MessageLabs said that spam vendors continue to send out a huge volume of junk mail via botnet-infected systems, despite efforts to shut them down.
The increased prevalence of botnets and their tendency to be used for spamming purposes would go a long way to explaining why spam still continues to account for over 90% of all email traffic around the world.
Of that, 83.2% came via botnets with the single biggest offender being the Cutwail botnet which was responsible for almost half of that figure.
Cutwail is believed to control as many as 2.1 million machines, primarily in the US, Brazi and Korea who are all noted as being botnet and malware hotspots.
After Cutwail the next biggest offender was Mega-D Trojan, responsible for about 10% of botnet spam.
The third and fourth largest botnet spam networks were Grum and Rustock, responsible for 6% and 4% of such spam respectively.