While the numbers remain high, global spam fell to the lowest level in three years, according to the latest report from Symantec.
Just a bit over 70 percent of all email was spam, a lower number than a few years ago, when it was well over 90 percent. Symantec calculated the percentage by analyzing 8 billion messages it processed a day last month, according to the company’s MessageLabs Intelligence Report.
Spam volumes dipped in March after Microsoft, law enforcement and other companies joined forces to take down Rustock, a large botnet responsible for sending up to 30 billion spam messages per day.
“Ever since then, nothing really filled the void,” said Andy Watson, a senior software engineer at Symantec.
Botnets increasingly have come under law enforcement scrutiny. Other botnets including Coreflood and Kelihos went down this year, and officials dismantled two major ones, Waledac and Bredolab, in 2010. A large affiliate spamming network called Spamit also shut down last year.
Watson said spammers may be putting more effort into social media sites because there is a better return. Spam links on services such as Twitter and Facebook can spread through users clicking on the links, Watson said.
Social-media spammers are continuing to set up their own URL shortening services, often with open-source software. By using a URL shortener, a user is less likely to see the link may lead to a questionable website.
Watson said the current largest spamming botnet is “Grum,” which is sending about 25 percent of the world’s spam. Grum has been around for a while and Symantec ranked it as the second-most active botnet last year, comprising up to 470,000 infected computers.
The U.S. is the biggest source of spam, sending 28 percent of the total number of messages, followed by India at 9 percent; Russia, 5.7 percent; Brazil, 4.3 percent and China at 4 percent, Symantec said. The most popular topics for spam messages are hawking pharmaceuticals, watches and jewelry, unsolicited newsletters and adult-related content.