The command and control centres behind the infamous Storm botnet have been eradicated or abandoned, leaving the former tempest a mere gust.
The threat landscape continues to rage, however, with the Mega-D botnet pumping out up to 30 percent of the world's spam.
At its peak, Storm accounted for 20 percent of the world's spam and used valentines day messages as a conduit to infect end user machines.
It declined over the past year as rival botnets Mega-D, Srizbi, Pushdo and others stole zombie recruits from its army, while security vendors ramped up the attack on the infected nodes that support it.
The botnet accounts for less than 1 percent of global spam now, according to security vendor Marshall.
Lead threat analyst for the company's TRACE anti-virus research team Phil Hay said the botnet may have declined due to its age, infamy or vulnerability.
“The creators of Storm [may] have abandoned it in favour of a newer botnet that they have created. It seems unlikely that Storm’s creators simply gave up and went home,” Hay said.
“Storm was the most successful botnet of its type and established the basic template for developing a spam empire that other botnets have since copied. Whoever was behind Storm really set the benchmark at the time for the kind of scale that was achievable with a spambot.
“They also led the way in using self-perpetuating malicious spam to grow the botnet — they used every social engineering trick in the book and invented quite a few of their own.”
The enormity of the Storm botnet lead in part to its decline as its eradication became a priority of white hat security researchers and vendors.
The largest botnet to date, Mega-D, has borrowed a few tricks from Storm, such as operating in Asian countries typified by high broadband penetration and poor use of anti-virus, using Trojans to dodge signature-based removal techniques and proliferating over peer-to-peer networks.
Industry speculation suggested the botnet's processing capacity rivalled the world’s top supercomputers, and infected up to 10 million zombie computers, however Hay suggests Storm had between 500,000 and 1 million nodes at its peak.
Some dying zombies are still trying to communicate, the security vendor reports, but are failing without a head.
Storm Timeline — credit to Marshall TRACE Jan 2007: Storm botnet comes to prominence with the headline “230 Dead as Storm Batters Europe” and rapidly infects hundreds of thousands of computers in a matter of days. Feb 2007: Storm’s next campaigns feature malicious executable attachments, but the Storm controllers quickly change tactics to drive-by malware provided through URL links when they realize that attachments are often detected by anti-spam and anti-virus solutions. Feb-Sep 2007: Storm uses fast flux DNS to avoid detection and changing malicious spam campaigns to infect up to 1 million computers. Storm’s self-perpetuating malicious spam campaigns establish the templates for other would-be spammers to develop their own botnets. Sep 2007: Storm has become the single biggest spam producer by volume pumping out 20 percent of the world's spam. This is the peak of Storm’s dominance. Microsoft targets Storm with the Malicious Software Removal Tool, cleaning about 275,000 infected computers in the first month. Oct 2007 – Jan 2008: Storm responsible for about 2 percent of global spam. Microsoft claims credit for reducing the Storm threat with MSRT. Jan-Sep 2008: Storm rarely exceeds 1 percent of the global spam statistics, while the top botnets routinely exceed 20 percent of spam and cumulatively account for more than 90 percent of spam in circulation.