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By: Robert Lemos
On July 9, nearly 300,000 PCs will find themselves dazed and confused when the DNSChanger botnet is shut down for good. These systems will no longer be able to look up common Web destinations, such as Facebook and Google.
Compromised by the DNSChanger bot software, the infected computers reroute all their domain-name requests-an act that turns domains such as “eweek.com” into the IP addresses understood by routers-through servers that had been owned by criminals. Since late last year, however, the Internet Systems Consortium has run the servers on behalf of U.S. law enforcement, which took control of the domains, ensuring that infected systems are not redirected to malicious sites. Yet, on July 9, those Domain Name System (DNS) servers will be shut down with the expiration of the court-ordered takeover. After that, compromised computers’ requests for Internet addresses will go unanswered.
That’s not a bad thing, says Gunter Ollmann, vice president of research for network protection firm Damballa. Turning off the service may disrupt the computers’ operation enough to finally alert the users.
“As an industry, we have tried just about everything,” said Ollmann. “And, frankly, the devices that are still victims today, that are still communicating, if they haven’t managed to notice everything-the updates, the alerts, and haven’t been secured-then I don’t think there is much more that can really happen.”
In November 2011, the FBI announced the arrest of six Estonian nationals and a Russian citizen for operating the DNSChanger botnet. At the time, they estimated that the program had managed to infect a cumulative 4 millions systems in 100 countries, including half a million computers in the United States. At the time of the takedown, computers at more than 800,000 IP addresses contacted the formerly malicious DNS servers on a daily basis. On July 4, that number dropped to a low of 277,000, according to data from the DNSChanger Working Group.
With more than a third of the once-compromised systems still showing signs of infection-and computers at some 12 percent of the Fortune 500 company among them-enterprises should be taking the problem more seriously, said Dan Brown, senior security researcher at digital protection firm Bit9. A DNSChanger infection is a good indicator that other malware is likely inside your network.
“Malware discovered in a corporate network needs to be paid close attention because it indicates a chink or perhaps a gaping hole in the corporate malware defenses,” Brown wrote in a blog post about DNSChanger. “If you are one of the 12 percent of Fortune 500 companies estimated to still be infected with DNSChanger, then it’s likely that your corporate security could benefit from some serious scrutiny.”
Companies in the United States are a major part of the problem. There are still nearly 70,000 computers in the United States-about a quarter of the worldwide total-that continue to harbor DNSChanger infections. Considering that Internet service provider, Google, Facebook, OpenDNS and other infrastructure companies have attempted to alert infected users, that number should be lower.
Yet, while companies should take security more seriously, DNSChanger is now little more than a punch line, Brown wrote.
“If you should find that one or more systems fail to resolve domain names following Monday’s shutdown, don’t panic,” said Brown. “This isn’t the beginning of a major malware campaign, it’s just the sound of DNS Changer going ‘pop!'”
Computer users who want to check if their system is infected should go to the DNSChanger Working Group’s site.