Computer scientists in the United States have condemned a court order that blocks three undergraduates from the Massachusetts Institute of Technology in Cambridge from discussing aspects of their research on the security of Boston's transit system.

The Massachusetts Bay Transportation Authority sought the order to prevent the students from giving a talk entitled "Anatomy of a Subway Hack" at a major convention in Las Vegas, Nevada. The talk exposed flaws in the transit system's 'smart cards', which are used for electronic ticketing.

In a letter supporting the students, 11 leading computer scientists warn that such restraining orders "will stifle research efforts and weaken academic computing research programmes".

As Nature went to press, a decision on whether to lift or amend the order was pending.