US investigators trying to catch those behind the Conficker worm outbreak that has infected millions of Windows machines since late last year requested that a security researcher scheduled to reveal the latest on 'The Conficker Mystery' at the Black Hat conference on Thursday go light on details. It's not clear which investigative organisation made the request.

A source close to F-Secure confirmed that Mikko Hypponen, the company's chief research officer, was asked not to divulge details about the worm's origins and the Conficker gang's motives.  The change in Hypponen's talk, 'The Conficker Mystery', was first reported by Reuters

Earlier in the day, F-Secure's blog said Hypponen would be speaking about Conficker (also known as Downadup), a worm that the company has tracked closely. 

The last-minute change of plans for Hypponen is nothing new at Black Hat, which has been the site of numerous speech-blockings and speech-blocking attempts, including that of a researcher Cisco sued because he was to reveal a flaw in the company's IOS code. 

Conficker's culprits are also the target for a $250,000 bounty offered by Microsoft.

See also:

Conficker IE bug will spread quickly

Network World