Anti-spam firm Ironport noticed spam mail levels dropped by 70 percent since McColo, a firm believed to have spam gangs as clients, was taken offline on November 11. Unfortunately, it's just a temporary drop as it's believed the spammers will quickly move to places where there is less scrutiny.
"It is an unprecedented drop but will be a temporary outage as the networks move from North America to places where there is less scrutiny," said Jason Steer, a spokesman for Ironport.
The Washington Post has been gathering data on McColo for the past four months and passed the information to its internet service providers, Global Crossing and Hurricane Electric.
Both decided to pull the plug on the firm on Tuesday.
It is believed that it hosted gangs running botnets - networks of computers that have been taken over by criminals to send malicious software and spam.
According to MessageLabs, botnets are responsible for over 90% of spam.