Staff at the Ministry of Defence and the military leaked secrets on social networking sites and forums 16 times in the past 18 months.
Ten people at these organisations have been disciplined for misusing sites including Twitter.
The leaks were disclosed after PR company Lewis made a Freedom of Information Request to the MoD.
The MoD did not reveal what type of leaks were made or the disciplinary action it took against staff who misused social networking sites.
Lewis PR said, "There are no rules banning MoD staff from joining online social networks in their personal lives or posting blogs and comments. However, the department's own code tells employees: 'Remember you are a member of HM Forces / MOD civil servant. Observe the same high standard of conduct and behaviour online as would be expected of you in your professional or personal life'."
IT directors must put policies in place to ensure that social media is not used by staff in a way that can be detrimental to the employer.