Just four bits of information gleaned from a shopper’s credit card can be used to identify almost anyone, researchers have found.
The study in the journal Science analysed three months of credit card records for 1.1m people in an unidentified industrialised country.
Ninety percent of individuals could be uniquely identified using just four pieces of information, such as where they bought coffee one day or where they purchased a new jumper or pair of shoes.
In other words, credit cards use was just as reliable at identifying someone as mobile phone records, the study found.
Knowing the price of a transaction could boost the risk of re-identification by 22pc.