Fraudsters are exploiting a security loophole to target Sainsbury’s shoppers and steal their Nectar points. Some shoppers are discovering that their points have been spent in stores that they have never visited and others have lost points while their physical loyalty card remains in their wallet. They insist that they have never shared security details with anyone. In some cases, criminals have been able to spend more points than the cardholder had saved, resulting in a negative balance similar to being overdrawn. Security experts say hackers are using unscrupulous online barcode generators to hack into accounts and steal Nectar savings. The scam means shoppers who are unaware their account has been compromised could end up saving points on their card for weeks or months without any benefit. That is because any new points they earn will go towards topping up this negative balance. Nectar, which is owned by Sainsbury’s, allows its 18 million-plus users to collect points on groceries and its sister brands Argos and Habitat, plus at Esso petrol stations and on eBay. For every £1 spent in store or online you typically earn one point, which is worth 0.5p. The loyalty club has soared in popularity since the...