US soldiers have been warned over using social media to tag photo’s potentially giving away their location to the enemy and putting their lives in danger.

The threat of ‘geotagging’ has been highlighted by US military authorities; the technology built into most smartphones can now show where a photo was taken.

‘Today, in pretty much every single smartphone, there is built-in GPS,’said US Army spokesman Steve Warren.

‘For every picture you take with that phone, it will automatically embed the latitude and longitude within the photograph.’

This is not a new problem, it has been highlighted before: In 2007 rebels in Iraq used geotags embedded in photographs posted on Facebook to locate helicopters at a US base. Four helicopters were destroyed in an attack.

It’s not just Facebook; soldiers have also been warned about posting pictures on other social media sharing sites such as Foursquare and Gowalla.

Staff sergeant Dale Sweetnam said Facebook’s new Timeline design, that shows more information about past activity and therefore adds risk because it can display a map of all he locations the person has been tagged in.

‘Timeline presents some unique security challenges for users who tag location to posts,’ he said.

‘A good rule of thumb when using location-based social networking applications is do not become friends with someone if you haven’t met them in person,’ Sweetnam added.

‘Make sure you’re careful about who you let into your social media circle.’

The Ministry of Defence have also warned the British Military of the possible threat caused ‘geotagging’ on social networking sites.