An expected activation of the Conficker.c worm at midnight on April 1 passed without incident, despite sensationalised fears that the internet itself might be affected, but security researchers said users aren't out of the woods yet.
"These guys have no designs, I think, on taking down the infrastructure, because that would separate them from their victims," said Paul Ferguson, a threat researcher at antivirus vendor Trend Micro, calling the technology and design of Conficker.c as "pretty much state of the art".
"They want to keep the infrastructure up and in place to make it much harder for good guys to counter and mitigate what they've orchestrated," he said.
Conficker.c was programmed to establish a link from infected host computers with command-and-control servers at midnight GMT on April 1. To reach these control servers, Conficker.c generates a list of 50,000 domain names and then selects 500 domain names to contact. That process has started, researchers said.
Exactly how many computers are infected with Conficker.c is not yet known, but the estimated number of systems infected by all variants of the Conficker worm exceeds 10 million, making this one of the largest botnets ever seen.
While infected computers have started reaching out to command servers as expected, nothing untoward has happened.
"We have observed that Conficker is reaching out, but so far none of the servers they are trying to reach are serving any new malware or any new commands," said Toralv Dirro, a security strategist at McAfee Avert Labs, in Germany.
This may just mean the people who control Conficker are biding their time, waiting for researchers and IT managers to relax their guard and assume the worst is over.
"It would be pretty stupid for the guys running Conficker to use the first possible opportunity, when everybody is very excited about it and looking at it very carefully," Dirro said. "If something was going to happen, it would probably happen in a couple of days."
Time is not on Conficker's side. The worm can be easily detected and removed by users. For example, if a PC is unable to reach websites such as McAfee.com, Microsoft.com, or Trendmicro.com that is an indication that the computer may be infected.
In addition, IT managers can easily spot traffic coming from odd domain names and block access to the computers on their company networks. "The longer criminals wait, the less infected hosts they've got," Dirro said.
Additional help comes from a loose coalition of security vendors and others called the Conficker Working Group, which has banded together to block access to domains that Conficker is trying to communicate with. But it's not immediately clear whether those efforts, which have been successful at blocking earlier versions of the worm, will be effective against the activation of Conficker.c.
"We can't really say how successful the attempts at blocking them or not routing them are," Dirro said. "That's something we'll see when the first domain actually starts serving malware, if at least one starts doing that."
Despite the uneventful passing of the activation deadline, the threat presented by Conficker remains real.
"These guys are very sophisticated, very professional, very determined and very measured in how they implement and make changes to things," Ferguson said, adding that Conficker.c is better defended and more survivable than previous versions of the worm. "This activation on April 1 was probably just arbitrary and picked to cause hysteria."
At some point, the people behind Conficker.c could try to generate revenue from the botnet they've created or they could have other intentions.
"The big mystery is that there's this big loaded gun out there, this network of millions of machines that's under the control of persons unknown," Ferguson said. "They've given no indication of what their motives are other than toying with people."