Big data — huge data sets that are often made publicly available to anyone who wants to analyze it — are supposed to be anonymous. The idea is to leave out key pieces of information about the people involved, such as name or home address, and leave only the larger trends.
But such specifics are not needed to reveal exactly who you are, according to researchers who were able to identify "anonymous" participants in a big data set 90% of the time.
The study — published in the journal Science — posits that researchers were able to identify "anonymous" shoppers from a big-data set based on credit card metadata: vague things such as the type of venue (a gym, for example) or the amount spent on a purchase.