Security researcher Dragos Ruiu has been painstakingly untangling a weird, scary piece of malicious software that compromises the BIOS of the computers it attacks, allowing it to infect machines with different operating systems. He's dubbed it "badBIOS" and has seen it infect machines that aren't connected to the Internet. It appears that its initial vector may be a USB exploit, spreading by memory stick, but after that, it appears that it continues to communicate with other infected machines by ultrasonic networking through its hosts' mics and speakers (!). On Ars Technica, Dan Goodin has a deep dive into the strange, freaky world of badBIOS.
Ruiu said he arrived at the theory about badBIOS's high-frequency networking capability after observing encrypted data packets being sent to and from an infected machine that had no obvious network connection with—but was in close proximity to—another badBIOS-infected computer. The packets were transmitted even when one of the machines had its Wi-Fi and Bluetooth cards removed. Ruiu also disconnected the machine's power cord to rule out the possibility it was receiving signals over the electrical connection. Even then, forensic tools showed the packets continued to flow over the airgapped machine. Then, when Ruiu removed internal speaker and microphone connected to the airgapped machine, the packets suddenly stopped.
With the speakers and mic intact, Ruiu said, the isolated computer seemed to be using the high-frequency connection to maintain the integrity of the badBIOS infection as he worked to dismantle software components the malware relied on.
"The airgapped machine is acting like it's connected to the Internet," he said. "Most of the problems we were having is we were slightly disabling bits of the components of the system. It would not let us disable some things. Things kept getting fixed automatically as soon as we tried to break them. It was weird."
Meet “badBIOS,” the mysterious Mac and PC malware that jumps airgaps [Dan Goodin/Ars Technica]