Rob Cotton, CEO of NCC Group, said: “When working undercover, you obviously need to maintain a low profile at all times, and that means having no images in the public domain, or being association with any person or organisation.

“When you have a Facebook profile, you are immediately doing just the opposite, and furthermore, opening up a Pandora’s box of online traceability that you can’t ever truly close. This extends to associations too – do you know what your partner, child or friend is writing about your life?”

Infosecurity notes that the new chief of the MI6, Sir John Sawers, ran into that exact problem when his wife posted personal family pictures on her Facebook profile making them available to ‘friends’ and millions of members of the London network on Facebook, BBC has reported.

NCC Group’s Cotton warned that people should err on the side of caution when it comes to even deciding on having a Facebook or other similar profile at all, and especially when it comes to aspiring spy recruits:

“The problem for national security staff is that once these details are out there, it is very difficult to erase them, and the wrong details in the wrong hands could actually lead to a life or death situation”, he said.

“For those in high-risk roles where information is like currency, something as innocuous as updating your profile with the wrong information could jeopardise a whole mission. Would-be spies out there should think carefully about the trains they are leaving in cyber space now – they’ll only come back to haunt you later”, Cotton warned.