Not sure it does actually prevent fraud. I recently moved and change my billing address and zip on all my cards, but not in my brain. When asked for my zip, I sometimes automatically say the one where I used to live. About 1/4 the time the old zip (2 years now) works and about 3/4 of the time it doesn't (NY, NJ and CT area). Same card. So it must depend to some extent on the interface with the vendor. If it was really going to prevent fraud it should never work when I use the old zip.