Two major internet service providers (ISPs) cut off internet access to the company McColo.com on Tuesday. Carole Theriault, of internet security firm Sophos called it an 'unprecedented' move.
It is believed the California-based company had a client list that included some of the world's largest cyber-criminal gangs who bombarded computers with unwanted messages.
Online security firms estimated that spam rates fell up to 75 per cent shortly after the company's servers were disconnected.
Although the levels have picked up again, the drop is being seen as strong evidence that a significant slice of the world's spam was coming from McColo.
'McColo Corp had a number of criminal organisations they were turning a blind eye to,' Jason Steer, product manager at IronPort, told vnunet.com.
'It was responsible for spam but lots as other things as well, even down to the level of child pornography.'
However, Steer does not believe that the shutdown will affect spam in the long term, saying that spammers will find other outlets.
Spam accounts for about 90 per cent of all e-mails send to computers around the world. U.S researchers recently found that spammers could turn a healthy profit despite only getting one response for every 12.5million emails they send.
The McColo web page is currently down, but the company can go online again if they find another willing ISP.
Source:Dailymail