The US marine corps have banned the use of social networking sites, after officials expressed concern about potential security risks. An order sent out to marines on 4 August informed them that they could no longer use sites including Facebook, MySpace and Twitter in case enemy groups used the information they contained to their advantage. The move is being seen by some as a signal that the Pentagon could enact a blanket ban on social networks across the entire military system. Last year the Pentagon used a fresh tactic to try and control the flow of information by launching TroopTube — a military-sponsored version of YouTube that allows serving personnel to share videos with only their friends and family members. All videos placed on the site must be checked by a Department of Defense worker before they are approved.