GCHQ, the UK communications spying centre, has launched a code-breaking competition via social networks as part of a recruitment drive.

The challenge, a visual code on a dedicated website canyoucrackit.co.uk, has been posted onto blogs, forums and social networking sites such as Facebook and Twitter.

"The target audience for this particular campaign is one that may not typically be attracted to traditional advertising methods and may be unaware that GCHQ is recruiting for these kinds of roles," a GCHQ spokesperson said.

Once the code has been cracked, successful codebreakers will receive a keyword and an invitation to apply for a role at GCHQ's.

All applicants to GCHQ must be British Citizens, however, any individuals who have hacked illegally before would not be eligible to apply.

The challenge has been live since 3 November and will continue until 12 December.

GCHQ has previously used unconventional channels to recruit new talent. In 2009 it placed recruitment messages on the Xbox Live network so that they appeared during video games such as Assassin's Creed and Call of Duty.