The advantage of using barcode technology is that it is cheap and easy to generate the credential and it can easily be applied to cards or other items. However the same affordability and simplicity makes the technology susceptible to fraud, because fake barcodes can also be created cheaply and easily, for example by photocopying real ones. One attempt to reduce fraud is to print the barcode using carbon-based ink, and then cover the bar code with a dark red overlay. The barcode can then be read with an optical reader tuned to the infrared spectrum, but can not easily be copied by a copy machine. This does not address the ease with which barcode numbers can be generated from a computer using almost any printer.
1 Based on the level of net new purchases (purchases less credits) that are posted to your Gas Advantage Mastercard account in any monthly billing period, you will be entitled to a discount on each litre of gasoline or diesel fuel that is purchased for a motor vehicle at Canadian Tire Gas Bars during the following monthly billing period and that is charged to your Gas Advantage Mastercard. The discount that you receive in a billing period will be reduced to 2¢ per litre after you have made purchases of more than $500 for gasoline, diesel fuel or any other sundry items at Canadian Tire Gas Bars during that billing period using your Gas Advantage Mastercard. For complete program details please read the Canadian Tire Gas Advantage Mastercard Terms and conditions.
In 1880 the American stage mentalist Washington Irving Bishop published a book revealing how mediums would use secret codes as the trick for their clairvoyant readings. The Seybert Commission was a group of faculty at the University of Pennsylvania who in 1884–1887 exposed fraudulent mediums such as Pierre L. O. A. Keeler and Henry Slade. The Fox sisters confessed to fraud in 1888. Margaret Fox revealed that she and her sister had produced the "spirit" rappings by cracking their toe joints.