Attempted fraud

I was contacted by one of my credit card providers this evening to be told they had blocked a suspicious online transaction on my account - £789 at John Lewis. I'm glad they did, because it was absolutely nothing to do with me. The card has now been blocked, and a replacement is on its way. This type of thing has only happened to me a handful of times before, but it is always unsettling and makes me very nervous for quite a while afterwards.