The advisory was circulated in a memo obtained by CBC News. It warns soldiers not to appear in uniform in online photos and not to disclose their military connections.
"Al Qaeda operatives are monitoring Facebook and other social networking sites," the memo says.
"This may seem overdramatic … [but] the information can be used to target members for further exploitation. It also opens the door for your families and friends to become potential targets as well."
The Defence Department says it is also concerned with postings of photos and information from the battlefront in Afghanistan.
how stupid do you have to be to make your facebook profile wide open and publicly accessable?