For most consumers, it's a familiar process: A new credit card arrives in your mailbox, you open the envelope, and the card bears a sticker reading, "Please call from your home phone to activate your card." Until then, your brand new credit card is as useless as a paperweight -- and just as secure, right? The startling truth is that while some unactivated cards are automatically declined, many others sail through a purchase without a hitch.

"Very few banks send out a card that can't be used, at least in low-risk situations," says Scott Stevenson, founder and CEO of Eliminate ID Theft, a credit protection service.

"But I'd bet most Americans think you cannot use a card unless you call and activate it." 'It went through' Linda Pack of Norfolk, Virginia, is one of the few who already knew that activation wasn't necessary.

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Activation is a security measure so that we know the customer actually got the card." Safe and sound To stymie an attempted card theft, your issuer may ask questions to which only you know the answers.

A customer service representative may also compare the phone number you're using with the one in your application, a reason why some activation stickers specify that you should call from your home number."Although people think that stealing stuff out of a mailbox is an arcane way of identity theft, actual physical theft is still one of the largest categories of how IDs get stolen." And these days, it's easier than ever.A potential crook just has to rifle through your mail, grab the envelope with a credit card -- easy to identify because they come in similar envelopes, usually from a processing center, and you can feel the card inside -- and activate the card.The editorial content on Credit is not sponsored by any bank or credit card issuer.The journalists in the editorial department are separate from the company's business operations.If you activate your card online -- an option offered by an increasing number of banks -- you'll need to log into your online banking account; that, in itself, can serve as another way to authenticate that you're the rightful owner of the credit card.