If you thought your electronically secured hotel room was safe, think again - because security experts have revealed that electronic lock systems found in global hotel chains can be hacked, allowing thieves to break into rooms without a trace.

The revelation comes from a group of researchers who hacked a lock system to produce a master key card that could open any door in the building, MailOnline Travel reports.

It has raised fears that thieves could exploit these systems to make room key cards "out of thin air".

The research was conducted by Finland-based cyber security company F-Secure, which hacked a system called the Vision by Ving Card made by the world's largest lock manufacturer, Assa Abloy. It's a system that's used to secure millions of hotel rooms around the world.

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The hack involved taking an ordinary electronic key card and using a small hardware device to read the information on it to produce multiple keys to the hotel.

These were then tested against multiple locks and within minutes the device was able to generate a master key that could open any door in the building.

The researchers said that even an expired key from a stay five years ago will work, along with cards that are used to access utility spaces such as garages or closets.

Although F-Secure stressed that during the research no hotel rooms were actually broken into and that the attack tools were not made available, Tomi Tuominen, the practice leader at F-Secure, said: "You can imagine what a malicious person could do with the power to enter any hotel room with a master key created basically out of thin air."

He added, however, that he didn't know of any group performing this attack in the world right now.

The researchers' interest in hacking hotel locks was sparked a decade ago when a colleague's laptop was stolen from a hotel room during a security conference.

When the researchers reported the theft, hotel staff dismissed their complaint given that there was not a single sign of forced entry, and no evidence of unauthorised access in the room entry logs.

The researchers decided to investigate the issue further, and chose to target a brand of lock known for quality and security.

It took a thorough understanding of the whole system's design to identify small flaws that, when combined, produced the attack.

The research took several thousand hours and was done on an on-and-off basis, and involved considerable amounts of trial and error.