A botnet blamed for harvesting sensitive documents from dozens of US government agencies and contractors, has struck according to security experts.
The botnet, dubbed "Kneber" by Alex Cox, principal research analyst at NetWitness, was behind a campaign of fake Christmas e-mails waged two weeks ago against government workers. NetWitness deals in advanced threat detection technologies, and conducts post mortem network forensics for firms that have been hit with attacks or data breaches.
According to Brian Krebs, a prominent security blogger who first reported the attacks, the messages duped dozens of government employees and contractors into installing malware, which then rummaged through their machines looking for Word, Excel and PDF documents.
Krebs, who had access to the hackers' repository, found documents belonging to the National Science Foundation, the Massachusetts State Police and a federal agency that provides foreign aid to countries in Africa, Central America and elsewhere.
Cox said it was almost certain that the attacks were launched by the same person or persons who had infected more than 75,000 computers with a variant of the Zeus Trojan horse. Cox pegged the variant, and the resulting army of hijacked Windows PCs, as "Kneber" after the name used to register several of the malware-serving Web domains.
Those attacks started in 2008, but were only uncovered in February 2010. Then, NetWitness determined that computers belonging to more than 370 U.S. companies and government agencies were infected.
In both incidents, a double-barreled attack first installed the Zeus variant, then followed with a much smaller payload composed of a custom Perl script that had been converted to an executable using Perl2Exe, said Cox. The Perl-based malware was the component that vacuumed up documents.
"The only other time we've seen [the latter] used was in February ," he added, talking about the Kneber research that NetWitness did 11 months ago.
A code "fingerprint" analysis showed that the February and December payloads were a 95.8% match, and the way they worked was identical. "Both look across the [compromised PC's] hard drive and collect Word, Excel and PDF documents, then upload them to a server in Belarus," Cox said.
And, as in February, the December attacks were aimed at government agencies, down to the spoofed "whitehouse.gov" address of the e-mails' sender.
Cox said it was impossible to know the motives behind either attack. "That's the ultimate question, isn't it?" he asked. "With attacks like this, there's always the possibility of an intelligence angle. There have been rumors, of course, that the Russian government turns a blind eye to hacking when they need something."
But he had other explanations. "This attack looks like it's about 20% successful, which means that 20% of those who received the message were infected," Cox said. The hackers might be using that statistic to market their botnet to other criminals.
Or they may plan to use the information themselves.
"We're seeing a trend of [hackers] looking for additional avenues of attack," said Cox. In that scenario, the documents siphoned from victims could be mined to build even more effective social engineering attacks that would, for instance, sprinkle agency-specific acronyms or names in the bait messages.
"But ultimately, we don't know why they're collecting the information," Cox admitted.
The only thing about the newest Kneber attack that stunned Cox was its effectiveness. "We see new attacks all the time, but what surprised me here was that Kneber has been known for about a year, but people are still getting infected," he said. "Even a year later with an identical payload, it still worked."