101 things you were too embarrassed to ask about money

When there are so many worries about credit card fraud and identity theft, this doesn't seem an unreasonable concern. While we're shredding our bank statements and putting chopped up cards in separate bins, we're also expected to tell complete strangers on the phone our three-digit "card security code".

These are the numbers printed on the signature strip. When you use a credit card over the phone, you're increasingly asked for these three digits as proof that you actually have the card. And many online purchases won't take place without them.

But do we have any choice about whether we give these details?

According to the payment service APACS it isn't optional. If you won't give retailers the code, they don't have to sell you the goods over the phone or online.

In the longer term, it's likely to be replaced by a personal chip and Pin reader, attached to your computer. But at present, the security code is used to provide extra verification - asking for a detail that is on the card itself and wouldn't be known by someone who had picked up a receipt or a credit card statement.

But there is a specific warning about these codes. Fraudsters are ringing cardholders at home, pretending to be from their credit card companies and tricking people into giving their security code numbers.

Barclaycard says: "The security code should not be disclosed to anyone other than a) when you are satisfied that the retailer/issuer is genuine and b) when you are positive that you wish to proceed with a purchase."

So if you get an unexpected inquiry, ring them back to check. It's a case of don't call us, we'll call you.