The shockwave stemming from the extermination of a United States-based hosting provider which pumped out 75 percent of the world's spam has reached Australia.

McColo, a Californian-based company played house to some of the world's worst online criminal gangs and was booted off the Internet following an investigation by Washington Post security researcher Brian Krebs.

The company's online presence was extinguished yesterday after Krebs alerted McColo's access providers Global Crossing and Hurricane Electric earlier this week to the criminal material it was pumping out over their networks.

Sophos Asia Pacific head of technology Paul Ducklin said spam reaching its honeypots has plummeted by more than 75 percent.

"Complaints to your ISP against rogue traders on the Internet may often feel like a waste of time, but spectacular successes can sometimes be achieved. This makes all the hard work worthwhile," Ducklin said in a written statement.

"It would be naive to think that this is any sort of long-term victory. Spam volumes will surely ramp back up, so we're not declaring a Lab holiday.

"Call it a truism if you will, but the price of freedom is eternal vigilance."

Ducklin said spam levels can be dropped by attacking central nodes — a part of network theory where even extremely complex networks can be destroyed by eliminating the nodes with the most connections.