The suspected China-based hackers known as the "Comment Crew" are back at it again, a development likely to contribute to continued tensions between the U.S. and China over cyberattacks.
The security community has had the group under its watch for a number of years, but in February, its activity was exhaustively detailed in a report from computer security vendor Mandiant.
Mandiant's report said a specific Chinese military unit called "61398" waged a seven-year hacking spree that compromised 141 organizations. The report added to other long-running research from security companies and organizations into suspected state-sponsored hacking.
The Comment Crew laid low for a while following the report but is back hacking again, said Alex Lanstein, senior researcher for FireEye.
"They took a little breather, and they started back up," Lanstein said.
Following the intense attention in February, the group stopped using much of its command-and-control infrastructure. Instead, they started from scratch, directing malware at new targets.
"We didn't see them take control of any of the systems they had previously compromised," Lanstein said. "They started fresh with a whole new round of attacks."
Slip-up offers clue
The group, while skilled, has made mistakes, many of which were picked up by Mandiant. Continuing analysis of the Comment Crew's methods have also revealed another mistake the group made, which conceivably makes it easier to link together attacks to a single source.
Lanstein said FireEye found the Comment Crew made an error when compiling their malicious software programs. When an application, including malware, is written in a programming language, it must be compiled, or translated into machine-readable code.
In many instances, the Comment Crew forgot to remove the name of their particular coding project, called "Moonclient," evident when a program was decompiled, or reverted back to its original programming language.
Lanstein said the error showed that "you are dealing with humans on the other side of the keyboard," who are prone to make mistakes. "This is a mistake made over and over again," he said.
FireEye decided to release information on the error since so much had already been released on the Comment Crew, and it would make little difference now for computer security researchers tracking them since their tactics have changed.
"It's more difficult to track them now," Lanstein said.