HUNDREDS of thousands of people have tried to crack this brain- teasing puzzle from an intelligence and security agency, but no one has done it yet.

The puzzle was put out with the UK’s Government Communications Headquarters’ (GCHQ) traditional Christmas card to staff.

GCHQ is a security and intelligence organisation tasked by the Government to protect the UK from threats and works closely with MI5, and the Secret Intelligence Service (MI6). They also have relationships with many other government departments and agencies.

The first stage of the puzzle has been online for anyone to solve since December last year, and contains a grid-shading puzzle with instructions on how to complete it.

By solving this first puzzle, players will create an image that leads to a series of increasingly complex challenges.

Once all stages have been unlocked and completed successfully, players were encouraged to submit their answer via a given GCHQ email address by January 31, 2016.

The winner will then be drawn from all the successful entries.

The instructions for the first stage were: “In this first grid-shading puzzle, each square is black or white,” the GCHQ website states.

“Some of the black squares have already been filled in for you.

“Each row or column is labelled with a string of numbers. The numbers indicate the length of all consecutive runs of black squares, and are displayed in the order that the runs appear in that line. For example, a label “2 1 6” indicates sets of two, one and six black squares, each of which will have at least one white square separating them.”

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GCHQ has revealed nearly 600,000 people have successfully completed the first stage of the puzzle.

When completed correctly it creates a “quick response” or QR code which leads to the next stage of the challenge.

While around 30,000 players have reached the final stage, none have successfully completed the puzzle.

GCHQ Director Robert Hannigan also offered a hint: “It’s not as abstract as you think.”

A number of people have been “very close” but no one has been 100 per cent correct.

Dr Gareth Moore, puzzle author and creator of the website Brained Up, told Sky News UK the puzzle is “only difficult in appearance” and is just “a question of being patient”.

“In actual fact, a picture puzzle like this can actually be solved by considering each row and each column one by one,” he said.

The puzzle was designed to encourage people to make a donation to the National Society for the Prevention of Cruelty to Children., his chosen charity over the holiday season.

The complete solution to the GCHQ puzzle will be published on its website in early February.

Download a larger version of the first stage of the puzzle here.