Spammers are pumping out an increasing number of garbage messages as they regain their capacity to send spam through hacked PCs, according to the latest statistics released by Google on Wednesday.
Google releases quarterly statistics from its Postini antispam group. For the second quarter, spam volumes are up 53 percent over the first quarter of this year, said Adam Swidler, product marketing manager for Google Enterprise.
Compared to the same period a year prior, spam volumes are up 6 percent. Google posted more information about spam on its enterprise blog.
Google filters around 3 billion to 3.5 billion spam messages a day for its 50,000 or so customers. Spam volumes have been increasingly erratic as some ISPs notorious for allowing spammers to use their infrastructure have been taken offline, Swidler said.
Last month, the U.S. Federal Trade Commission persuaded a federal court to issue a temporary restraining order to shut down Pricewert, an ISP that did business under the names 3FN and APS Telecom. The FTC said Pricewert was entwined with child pornographers, hackers and malicious software developers.
Swidler said Google immediately noticed a 30 percent drop in spam following the shutdown. Pricewert's closure cramped spammers' capacity to send spam through compromised home computers that form botnets.
But in just a month or so, spam volumes have risen, due to spammers' efforts to gain more hacked PCs. Google noticed that June had the highest volume of spam messages containing malicious code designed to make a computer part of a botnet, Swidler said.
On June 18, Google said spammers sent more messages in a two-hour window than they usually do in 12 hours. That shows there's "clearly a lot of botnet firepower out there," Swidler said.
Google also saw an increase in image spam. The technique had fallen somewhat out of favor by spammers as security vendors modified their software to filter it. Swidler said it may be a sign new spammers are entering the game and recycling some of the toolkits used to create image spam.
"The bottom line is there's money to be made by the activities that these folks do," Swidler said.