HUNDREDS of former and some present Australian spies have posted information about their employment with intelligence agencies on the internet in what security experts have called ''a gift for foreign espionage''.

A survey by Fairfax Media has discovered more than 200 former and present intelligence officers who have disclosed their classified employment in profiles on LinkedIn, other professional networking sites and social media including Facebook and Twitter.

'A gift for foreign espionage' ... security experts have slammed the presence of international spies on social media. Credit:Louie Douvis

While many former and present officers have disclosed only the fact of their employment by agencies including the top secret Defence Signals Directorate and the Defence Intelligence Organisation, some have revealed significant details about their work.

These include employment at specific intelligence facilities, overseas postings and liaison with allied intelligence agencies, linguistic expertise indicating particular intelligence targets, and involvement with specific issues and information technology systems.