Study: Uptick in spam-sending zombie PCs in September
Compromised computers that send spam as part of their regular botnet activity increased dramatically in September, according to a Symantec study (PDF) released Monday.
The Symantec report follows a study from MessageLabs also illustrating the increased use of automated spam relays.
After seeing a 37 percent drop in botnet-related spam for August, Symantec reported a 101 percent increase in September. The growth appears to be focused in Europe, the Middle East, and Asia, with South Korea experiencing the largest increase at 4,236 percent. It was followed by Kazakhstan (761 percent), Romania (607 percent), Saudi Arabia (555 percent), and Vietnam (540 percent).
Compromised PCs sending spam had been part of the background noise until recently, when their usage surged in September.
(Credit: Symantec)In looking for a reason behind the one-month increase, Symantec speculated it had something to do with the increase in e-mail with sensationalistic news headlines that included links to downloadable malware. These include malicious spam campaigns emulating e-mail from CNN and MSNBC.
Turkey topped the list of countries hosting spam-sending compromised PCs, responsible for 12 percent of such traffic, according to Symantec. It was followed by Brazil (9 percent), Russia (8 percent), the U.S. (6 percent), India (6 percent), China (6 percent), Germany (5 percent), Argentina (4 percent), Poland (4 percent), and Thailand (3 percent).
As CNET's resident security expert, Robert Vamosi has been interviewed on the BBC, CNN, MSNBC, and other outlets to share his knowledge about the latest online threats and to offer advice on personal and corporate security. Listen to his podcast at securitybites.cnet.com or e-mail Robert with your questions and comments.
Seeing as most residential users do not run their own mail server, why not block it by default and unblock it on request?
This would drastically cut the number of machines that can be turned into zombies. Some ISPs do this but many don't.