It's happened to countless people: you talk about something with your friends, like a needing a new lawnmower or TV, and later that day an ad for that same product appears on your smartphone.
For years, iPhone and Android users have been convinced that their social media accounts are eavesdropping on their conversations—something that platforms like Facebook have long denied.
But new research from NordVPN suggests that, while your social media apps aren't listening to you, advertisers are.
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Apparently, ad companies are using a sneaky type of data monitoring called ultrasonic cross-device tracking to listen to background noise and serve up personalised ads to users.