You get a call from your bank saying there has been suspicious activity on your account. They read out your name, address and date of birth so you are happy it is a legitimate caller.

But you are talking to criminals who have used your date of birth as part of a web of verifying information to convince you they are someone else.

People’s DOBs are often held in online accounts after being entered as part of a sign-up process for a retailer, loyalty scheme, newsletter or online competition. In a recent hack of the online retailer Asos customers’ dates of birth were among the details taken by scammers.

Now cybersecurity professionals have warned people to resist entering a date of birth, or to put in a fake one, to limit the amount of personal data that is online, frustrating criminals’ attempts to “jigsaw” together personal profiles.

Jake Moore, an adviser for the cybersecurity company ESET, says information gathered during hacks can be sold on and used by scammers, either to trick people into trusting…