A Quick Response (QR) code is a two-dimensional barcode. It stores more information than a traditional one-dimensional line barcode. They were originally developed in the Japanese automotive industry, but have been adopted by other industries. QR codes were approved as an international standard by ISO in 2000. The latest specification can be found at https://www.iso.org/standard/62021.html.
QR codes can be found on some billboards, posters, handouts, and other advertising material. QR codes are also used frequently in transactions. You might see QR codes on train tickets or when sending and receiving cryptocurrency such as Bitcoin. Some authentication services such as two-factor authentication utilize QR codes for convenience.
QR codes are good for social engineering because a human can't tell just by looking at a QR code if it is malicious or not. Often...
