Microsoft is playing down the possibility that the speech recognition system in Windows Vista could be hijacked to delete files or perform other unauthorised actions.
Vista contains improved speech recognition technology, a factor which prompted security researchers to see if it was possible to create MP3 files on hacker websites or audio tracks distributed on P2P networks to issue spoken commands which takes control of PCs running Vista.
Microsoft said the exploit is technically possible but unlikely to be much of a threat in practice. The attack scenario relies on activation of the speech recognition feature (with a user's microphone and speakers switched on to receive commands) and for a user to be away from his desk, so that the mischief takes place without anyone intervening. Many PCs are left on all the time, so hitting unattended PCs on, for example, the trading floor of a bank simply by targeting them at night might be possible.
A number of security researchers and Vista geeks have already tested the approach and were able to delete files and visit, albeit with considerable difficulty, arbitrary websites. But Microsoft says a number of additional factors make attacks based on the approach implausible, if not impossible.
"It is not possible through the use of voice commands to get the system to perform privileged functions such as creating a user without being prompted by UAC for Administrator credentials. The UAC prompt cannot be manipulated by voice commands by default. There are also additional barriers that would make an attack difficult including speaker and microphone placement, microphone feedback, and the clarity of the dictation," Adrian, a Microsoft security researcher wrote on Redmond's security response blog.
"While we are taking the reports seriously and investigating them accordingly I am confident in saying that there is little if any need to worry about the effects of this issue on your new Windows Vista installation," he added.
The SANS Institute's Internet Storm Centre (ISC), disputes Microsoft's assessment of the potential danger posed by the feature. "Downloading and executing a local privilege escalation is still eminently possible, you just need a suitable 0-day local privilege escalation for Vista. Indeed, any way to download and run arbitrary code as a valid user is never good news, this one just happens to be from the 'neat trick' pile," ISC duty staffer Arrigo Triulzi writes. ®