Security researchers are in the dark about what will happen next week when the newest variant of Conficker, 2009's biggest worm by a mile, begins trying to contact its controllers.
"It's impossible to know until we see something that has a clear profit motive," said Joe Stewart, director of malware research at SecureWorks and a noted botnet researcher.
PCs infected with Conficker.c, the third version of the worm that first appeared late last year, will use a new communication scheme on April 1 to establish a link to the command-and-control servers operated by the hackers who seeded the malware. The date is hard-coded into the worm, which in turn polls any of a number of major websites, including Yahoo, for the date, said Stewart.
That tactic is just one of several designed to make it tough for security researchers to figure out what Conficker's all about, and more importantly, what it might do. "We had to trick it into thinking it's not only getting back the right page, but that it's getting the April 1 date," said Stewart, talking about the machines SecureWorks purposefully infected with Conficker.c.
"So far, we haven't seen any evidence [on those machines] of what it will do April 1," added Stewart, although that's to be expected. "It's not April 1 yet, so they're not going to put something online, where it might be found. In fact, it's almost a little risky for us to try to look for those sites, since it might give away that we have some bots in their network."
Symantec's Vincent Weafer, vice president of the company's security response group, agreed with Stewart that it's impossible to know ahead of time what stunt Conficker's controllers will pull next week. "Nobody has any real idea," said Weafer. "There's no indication of what it will do April 1."
Weafer characterised the Conficker.c update as one to "armour and harden the existing infections," and noted that the variant, unlike its predecessors, cannot spread to other PCs. "This variant is very defensive-oriented," said Weafer, "to make it less visible and more resilient."
Like Weafer, Stewart sees Conficker.c as a move to by the worm's maker or makers to consolidate what's already infected. "The big question is what's the end game?" he said. "Is it just as big as they want it to get?"
He also noted Conficker.c's tilt toward the sophisticated, seconding Weafer's opinion that the worm's makers are trying to stump both researchers and anti-virus software.
"This a very curious thing," Stewart said. "[The hackers] are more patient and more methodical than most. They're raising the bar, by a lot, in terms of what we have to do to figure out what it does, to block it, to clean it.
"It's not your typical type of e-crime," he said.
Conficker, which is also called Downadup by some security companies, first appeared late last year, and originally exploited a Windows vulnerability that Microsoft patched in an October 2008 emergency update. In early 2009, the next version - Conficker.b - infected millions of PCs in just a few days.