New South Wales police said a 17-year-old girl was helping her 72-year-old grandmother count her savings at the older woman's Sydney home May 24 and the teenager posted a picture of the large amount of cash to her Facebook page.
Police said two men armed with a knife and a wooden club entered the Bundanoon home of the girl's 47-year-old mother while she was home with a 58-year-old man and a 14-year-old boy.
The men demanded to speak to the girl about the cash and the mother informed her that the teenager no longer resided at the address, police said.
The men took a small amount of cash and personal property from the home, police said.
New South Wales police said the incident highlights the need for caution when posting photographs and personal information on social media sites.