(New Scientist) Dragos Ruiu first became suspicious when he was installing a new version of Apple's OS X onto his MacBook. Unasked, his laptop also started to update its BIOS – which boots up the OS and choreographs use of disc drives and memory. In the three years since, Ruiu's computers have continued to do strange things – even when unplugged and with the Wi-Fi and Bluetooth switched off. He now believes that hidden viruses on his machines are being controlled via ultrasound signals broadcast from one infected computer to another.
The incredible claims made by Ruiu, a respected computer security researcher from Vancouver, Canada, have sparked a row in the world of cyber security. Some doubt this sonic "backdoor" can be genuine – no one has yet tracked down computer code that can generate the audio. Although Ruiu's claim remains unproven, others say that audio-based malware is a very real possibility.