MILLIONS of computer whizzes have been trying to crack it as cyber spies on a GCHQ website.

After the Cheltenham-based intelligence service posted an online code and invited genius minds to solve it in the hope of finding a job, they received interest from around the world.

More than 2.4 million people visited the game, titled Can you crack it? in an attempt to bag one of 35 vacancies at the headquarters, in Cheltenham's Benhall doughnut.

Just 236 people managed to decode the numbers, with 179 submitting job applications as a result.

The challenge was aimed finding people with decoding and ethical hacking skills.

A grid full of 160 pairs of letters and numbers had to be decoded in seven hours in order for the contenders to make the grade.

Those who were successful were then directed to the agency's website and invited to apply for a job.

Computer geniuses cracking the code came from as far afield as Russia, the United States of America and Indonesia, although spy chiefs have revealed that some applicants did come from Gloucestershire.

A spokesman for GCHQ said the organisation had been pleased with the response.

He said: "The challenge exceeded our expectations in terms of the interest levels raised.

"While there were a number of people who tried to subvert the challenge and cheat the answer, those who have genuinely followed each of the stages have fed back to us that they found it highly challenging and engaging.

"Whether or not we do something similar in the future remains to be seen.

"GCHQ has a history of codebreaking and so the code challenge itself was not the innovation, but rather the way in which the social media was used to seed the recruitment message to its audience.

"It will need to continue to evolve its recruitment strategies to continue to attract the people with the right skills to protect UK people and interests.

"People from across the globe attempted the challenge.

"Reassuringly though we still had people from the local area attempting the challenge - and they do not already work for GCHQ."

GCHQ has experienced problems recruiting computer experts in the past.

Bosses have complained that they cannot compete with the huge salaries offered by big name technology firms such as Google and Microsoft.

The Government approved a package of perks and incentives to be handed out to consultants in an effort to stem the tide last month.

It came just weeks after GCHQ bosses were criticised by MPs on the Intelligence and Security Committee for the massive cost of the high-tech consultants drafted in to tackle the growing threat of online terrorism.

Some consultants are already believed to be earning average annual salaries of £145,000, compared with many permanent staff who earn less than £25,000 a year.

Stage 1: This starts with the main image on the canyoucrackit.co.uk site. To solve this stage it is necessary to identify that this is code that can be run by an Intel x86 compatible processor. After analysis, it is clear that this machine code implements the RC4 decryption algorithm, and is able to decrypt a block of data that is hidden inside the PNG file, in a comment tag. Once decrypted, this data reveals the location of stage 2 of the challenge.

Stage 2: This is a JavaScript programming challenge, with a cyber security angle. To solve this stage an implementation of a simple virtual processor is required. Some notes on the architecture are provided along with a block of data that can be analysed. Solving this stage will reveal the final stage of the challenge.

Stage 3: The final stage is a reverse engineering challenge. An executable file can be downloaded from the location revealed in stage 2. This executable parses a licence file – if it gets given a correct input, the challenge is revealed to be over, and a link to the ‘success’ page is provided to the participant.