A spate of thefts from American hotel rooms has been linked to an electronic 'hack' which can open an electronic lock used in four million hotel rooms worldwide.
The 'Onity' locks in Hyatt hotels in America were the victim of burglaries where the doors did not appear to have been forced.
A hacker published a guide to how to open the locks in July, but it's now thought that thieves may have developed pen-sized 'kits' which allow them to open doors easily.
Cody Brocious, 24, showed off a hack that allowed people to copy the "portable programmer" used to make master keys for Onity locks. Brocious's device cost less than $50.
Maker Onity released a 'fix' for the locks, but it requires physical attention - a long process for hotels with hundreds of rooms - and it's not clear how many of the vulnerable doors have been protected.
In America, 27-year-old Matthew Allen Cook was charged with a string of robberies at Hyatt hotels which seemed to exploit the vulnerability in the doors.
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Forbes magazine reports that Onity is asking hotels to shoulder some of the costs of replacing vulnerable locks - which could slow the process even further.
The simple electronic systems used to control locks and other equipment can be vulnerable to hackers.
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A test in America showed that computer controlled cell doors in prisons could be opened remotely by anyone with access to the system controlling them.
Kevin Haley, Director of Security Response at Norton, said "It’s just part of the way our infrastructure has evolved."