Spike in malicious spam could signal rebuilding of spambot networks
- By William Jackson
- Aug 17, 2011
In what could be a backlash against recent takedowns of spam botnets, researchers at M86 Security have reported what they call an epic surge in spam containing malicious attachments.
The volume of spam containing malware shot up in August to rates not seen in the past two years, the security company reported in a recent blog posting
. For the past year or more spam containing malware has made up a small percentage of spam, but during the second week of August it made up 13 percent and shot up to 24 percent on Aug. 15.
“There has been a slight increase in overall spam,” said M86 Product Manager Ed Rowley. “This subset has caused the increase.”
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Rowley said he suspects that the surge represents a rebuilding effort on the part of cyber criminals who have been licking their wounds from successful takedowns of botnets over the past two years. They still are trying to make money with fake antivirus scams and by stealing financial information, but “they are also trying to infect machines and increase the size of their botnets,” he said.
Law enforcement agencies and companies have been taking aggressive legal action against spammers recently. In March, the Microsoft Digital Crimes Unit was able to take down the Rustock botnet controlling more than 1 million infected computers, and in April the Justice Department obtained a court order to take down the Coreflood botnet by eliminating its command-and-control servers located in the United States.
And last year the FBI, in cooperation with cybersecurity experts and with law enforcement officials in the United Kingdom, Europe and Ukraine, busted a Zeus botnet ring believed responsible for illegally transferring $70 million from U.S. banks.
At the same time, there has been an increased in more sophisticated spear phishing attacks targeting high-value victims who can provide access to sensitive information and intellectual property.
The net result has been an overall decrease in spam and particularly in malicious spam. A recent white paper on e-mail attacks
from Cisco Systems reported that profits from traditional mass e-mail attacks had declined by 50 percent over the past year, which is reflected in a drop in spam volume from 300 billion a day in June 2010 to a mere 40 billion a day in June 2011.
But spam still dominates the e-mail landscape and we might see a regeneration of botnets. The current spate of attacks represents a change in quantity but not in quality, Rowley said. Most of the e-mails contain familiar exploits and recycled themes, including:
- FedEx deliveries (“Delivery failed. Please print out the invoice copy attached...”).
- Credit cards (“Your credit card is blocked! More detailed information in the attached file.”).
- Invoices (“As requested I give you the open invoices issued to you...”).
Rowley said he believed the current surge in attacks is timed to exploit the summer vacation season when more people are likely to be checking e-mail from home computers that might not have up-to-date antivirus and spam filters.
Filters consistently identify and block the majority of spam and most of the malware they contain exploit known vulnerabilities for which patches are available. “I don’t think they have been particularly successful,” Rowley said of the surge.
But the surge does emphasize the need to keep patches and antivirus up to date, and to use common sense when opening e-mail.
“The rules haven’t changed, but people still forget them,” Rowley said.