The Defence Force has issued a handbook to personnel with guidelines on how to use social networking sites.
It warns that even "the most trivial" information can be dangerous for friends and loved ones if posted online, due to technological advancements which can track users.
"It could even get someone injured or killed," the document says.
Piecing together information through the internet was unsurprisingly easy, and adversaries were very good at pulling together a complete picture of something "using a trail of information we leave online".
"So, avoid mentioning your rank, locations, deployments, dates, names, equipment and other capabilities.
"Don't tag photos with locations either deliberately or by accident ... "
The Defence Force (NZDF) said the handbook serves as a set of guidelines, and is not policy.
It said soldiers should talk with family and friends about using websites safely.
"For example, a family member's post might read: 'Missing Sally sooo much. She is going to be in Afghanistan at XYZ Camp near Bagram all Christmas - and not home for two month :( Really sad'.
"Help them understand that: 'Sally is posted overseas this Christmas. Really sad but can't wait till she's home' is a better - and safer - option."
The handbook also said Defence Force staff should avoid speaking negatively about supervisors, releasing sensitive information, or engaging unkindly with others.
A spokesman for the NZDF said today that its social media guidelines had been in place since 2010.
He said there were no specific incidents that prompted the book.
Instead, it was down to the changing nature of social media and advancements in technology like automatic location tagging in photos, and the NZDF saw a need to provide guidelines to "ensure our people are following a set process".
"NZDF operate a commonsense approach to social media," the spokesman said.
"We support our people telling their stories and experiences in Defence, although all content on social media should be treated as public or accessible by the public, and information that could break operational security requirements could possibly put people in danger.
"This handbook is designed so our people understand how to work safely on social media."
NZDF safe tips included:
• Disable the option to be tagged in online games
• Don't post sensitive information about where you are or who you are with
• Disable the GPS function on smartphones while on duty or deployed
• Check photos and videos before posting them online for anything that might reveal a location or your deployment