A top UK security expert has criticised the practice of issuing unsolicited credit cards.

Professor Ross Anderson of Cambridge University reports how his wife recently received a pre-approved, unsolicited Gold Mastercard from UK store Debenhams with a credit limit of more than £1,000 through the post.

The security implications, as well as the ethics, of these type of inertia sales irk Anderson. Following Debenhams' advice of cutting up the card and throwing it in the bin simply doesn't pass muster, he argues. For one thing, the UK's move to Chip and PIN on plastic cards as an alternative to signature-authorised transactions complicates the problem of disposing of unwanted plastic cards.

"The average customer has no idea how to ‘cut up’ a card now that it’s got a chip in it," he writes .

"Bisecting the plastic using scissors leaves the chip functional, so someone who fishes it out of the trash might use a yescard to clone it, even if they don’t know the PIN. The PIN mailer might be in the same bin.

"Here at the Lab we do have access to the means to destroy chips (HNO3, HF) but you really don’t want that stuff at home. Putting 240V through it will stop it working - but as this melts the bonding wires, an able attacker might depackage and rebond the chip," he adds.

Anderson suggests consumers ought to destroy unwanted cards with either a hack saw or a robust pair of tin snips. "This isn’t foolproof as there exist labs that can retrieve data from chip fragments, but it’s probably good enough to keep out the hackers," Anderson adds. ®