The phishing group -- named Avalanche by security researchers because of the large quantity of attacks it generates -- was blamed for more than 84,000 out of the nearly 127,000 phishing attacks tracked by the Anti-Phishing Working Group (APWG), an organization of companies and law enforcement agencies that tracks phishing activity in its semi-annual reports.
Avalanche has used slick automated tools to crank out phishing attacks quickly, setting up fake Web sites and then spamming potential victims with email messages designed to trick them into typing in their usernames and passwords.
The group has targeted about 40 institutions, including major U.S. and U.K. banks as well as online providers such as Yahoo and Google, said Greg Aaron, director of domain security with Internet infrastructure vendor Afilias, one of the authors of the report. "They were able to ramp up and they became very, very large," he said.
Spurred by this activity, the overall number of phishing attacks more than doubled in the last half of 2009 over the first half of the year.
Avalanche first popped up in late 2008, not long after the previous top phishing threat, Rock Phish, dropped off the scene. In fact, some antiphishing experts believe that Avalanche is simply the next generation of phishing tools designed by Rock Phish's creators. Researchers believe that Avalanche, like Rock Phish, is run out of an Eastern European country.
By October of last year, Avalanche was such a big problem that security companies and the firms whose users were being phished got together in Seattle to share information on the group and work out ways of fighting the problem.
Companies began sharing data that had previously been kept private, and groups were formed to keep track of new Avalanche domains, said Gary Warner, director of research in computer forensics with the University of Alabama at Birmingham. "Whenever any brand or member saw a new domain, we went straight to the registrars and began pounding them from a bunch of different sources," he said in an instant-message interview.
That helped the good guys take down fake sites much faster than before. "In five years now of working anti-phishing research, this was the most coordinated community effort I've ever seen," Warner said.
The registries also were able to be more proactive. "And the different registries that were getting abused began learning how to recognize the domains on their own," he said.
In early 2008, the average takedown time for a phishing site was 49.5 hours, Aaron said. In the last half of 2009 that had been cut down to 31 hours, 38 minutes. Avalanche domains, however, went down twice as fast, on average, as other phishing domains.
Right now, it looks like the group's work on Avalanche may be paying off.
In November, several unnamed security companies got together and took down Avalanche's infrastructure for about a week, Aaron said.
That takedown put a big dent in the number of phishing attacks for November, and following a brief rebound, Avalanche attacks have tapered off precipitously in the past few months, Aaron said.
He doesn't know how long this quiet period will last, however. "We don't know if they're going to fade away or if they're going to change what they're doing somehow and ramp back up again."