"As we feared, spammers have shown their resilience," Adam Swidler, senior product marketing manager for the company's message security network, told SCMagazineUS.com.
Spammers employed a new tactic in the first quarter of this year by sending out location-based spam, and also utilised some traditional techniques, such as attaching viruses to spam and socially engineering messages to take advantage of holidays and the current economic downturn, he said. By the second half of March, the seven-day spam average is back up to where it was pre-McColo - with spam again accounting for 94 to 95 percent of all email, Swidler said.
Global spam volume grew rapidly during the first quarter, increasing 1.2 percent each day on average, he said. The previous record-high rate of growth was one percent per day in the first quarter of 2008.
Those in the industry predicted it was only a matter of time before spam would rise to the levels it once was. André Di Mino, co-founder and director at volunteer watchdog Shadowserver Foundation, told SCMagazineUS.com in an email that he is not at all surprised that spam levels are back up.
"Spam is a very large and lucrative business," he said. "As such, it's not going to go away that easily. There are many other questionable or outright complicit hosting providers eager to pick up the void left by McColo."