During the Second World War, the British government famously released posters warning: "Careless talk costs lives." Now the IDF is running a contemporary equivalent campaign - against indiscreet Facebook posts.

Top brass have written to all commanders asking them to urge subordinates to be careful what they post on Facebook and other social networking sites.

It urges against posting photos taken on bases or pictures of soldiers which give away information about their role in the army, such as by revealing unit insignia, or where they live.

It also implores them not to write anything that details what they have been doing, or are set to do, in the army. In March the army cancelled a raid after a soldier who was meant to participate posted details about the planned operation on Facebook.

In November, pro-Palestinian activists published online a list of soldiers' names and photographs of 200 Israeli soldiers - some of them with home addresses - on a website that labelled them war criminals. The army believes that information came from websites.

Military spokesman Arye Shalicar said: "The Israel Defence Forces asks soldiers and reserve soldiers to watch out what they put on social media sites and not give away information which could harm the security of the soldiers themselves and the Israel Defence Forces."

On military bases there are posters with a mock Facebook page and images of Iranian President Mahmoud Ahmadinejad, Syrian President Bashar Assad and Hizbollah leader Sheikh Hassan Nasrallah with Facebook "friend requests" and a catch line: "You think that everyone is your friend?"