Spam levels have remained resolutely stable despite recent botnet takedowns, according to a survey from Google's email filtering business.
Google Postini reports no lasting effect from the recent takedown of spam-spewing botnet, such as Mariposa and Mega-D. The command-and-control servers associated with the Mega-D botnet were isolated towards the end of 2009, effectively decapitating one of the top-10 junk mail sources.
Early this year, government agencies and security firms teamed up to take-down several other botnet targets - including Waledac, Mariposa, and Zeus - using similar tactics. The operations are these botnets were either curtailed (Mariposa) or severely hampered in the process (Zeus).
These combined efforts have failed to make much difference in the volumes of spam circulating online. Spam and virus levels did dip down 12 per cent from a Q409 high but held "relatively steady" throughout the first quarter of 2010, Google Postini reports.
"This suggests that there’s no shortage of botnets out there for spammers to use," a blog post by Postini researchers notes. "If one botnet goes offline, spammers simply buy, rent, or deploy another, making it difficult for the anti-spam community to make significant inroads in the fight against spam with individual botnet takedowns."
The Google spam filtering division concludes that going after botnets is no more effective than the previous tactic of targeting rogue ISPs. The takedown of rogue ISP 3FN bought a temporary respite from the spam deluge for about a month. However, after Real Host, another ISP, was taken out months later spam volumes recovered after only two days. The marked difference was due to use of improved disaster recovery approaches by cybercriminals.
Google's conclusions are based on an analysis of spam volumes flowing into the email in-boxes of 18 million business users working for of 50,000 organisation protected by Postini's technology. Analysis of the junk mail traffic blocked by Google's technology also shows a 30 per cent increase in the size of individual spam messages toward the end of March - signs of a possible resurgence in the use of image spam - and the use of natural disasters (such as the Haiti earthquake) and celebrity gossip in a bid to persuade recipients to waste time on junk mail messages, some of which form the kick-off point of financial fraud.
The prevalence of malware within spam, which rose from 0.3 per cent at the start of 2009 to 3.7 per cent in the second half of last year, fell back to 1.1 per cent in the first quarter of 2010. ®