Would you share a stranger's post about a suspicious loan offer? Probably not. But what about one that asks for help reuniting a lost dog with its owner?

AFP's Johannesburg-based journalist spotted identical posts on seemingly local issues shared to hundreds of Facebook buy-and-sell groups, often thousands of miles apart.

By checking the edit history of posts pushing dubious banking apps or rent-to-buy homes, she discovered the tactic used to spread such scams. The posts originally contained emotionally-charged warnings or pleas for help, but they were replaced with ads once they attracted hundreds of shares.