"Right now, and I mean this instant, delete every digital trace of any menstrual tracking. Please."

This is a tweet that went viral in the wake of the repeal of Roe V Wade in the United States. Fearing a clamp down on reproductive rights, suddenly people were looking at their online data in a very new way. What does my fitness app say about the state of my body? What could be divined from the details of what I bought? What about the data of the people around me?

This is not the first time a sudden social or political change has thrown up potential problems of big data. But now we live in a world of data brokers, thousands of companies collecting, collating and sharing data around the world - and the data related to pregnancy is the most valuable of the lot. Which means, if there is a sudden change in reproductive rights, there’s a lot of data that could be mined for information if a broker sells it on.

Aleks explores what happens when freely given data suddenly becomes dangerous, if it’s possible to keep any secrets in an online maelstrom of information, and why we keep coming up against this problem again, and again, and again…