During red teaming assignments we are sporadically asked to attempt to gain access to certain physical “flags”. These flags could be the inside of a server room, or the workstation of a member of the management team. There are many different RFID card reading systems on the market. Unfortunately, the security they provide is often lacking. With this blog post we want to demonstrate how easy it is to bypass the card reader security mechanism when it is insufficiently secured. Specialised hardware is required to clone existing RFID cards, this hardware can easily be obtained and is relatively inexpensive. For this case study, we use the Proxmark3, which is a device developed by Jonathan Westhues that allows sniffing, reading and cloning of RFID (Radio Frequency Identification) cards. This guide is intended for educational purposes only and should not be used to bypass security measures without proper authorization.