Software Defined Radio has been quietly revolutionising the world of RF. However, the same revolution has not yet taken place in RFID. The proliferation of RFID/NFC devices means that it is unlikely that you will not interact with one such device or another on a daily basis. Whether it's your car key, door entry card, transport card, contactless credit card, passport, etc. you almost certainly have one in your pocket right now! RFIDler is a new project, created by Aperture Labs, designed to bring the world of Software Defined Radio into the RFID spectrum. We have created a small, open source, cheap to build platform that allows any suitably powerful microprocessor access to the raw data created by the over-the-air conversation between tag and reader coil. The device can also act as a standalone 'hacking' platform for RFID manipulation/examination. The rest is up to you! In this talk I'll cover the fundamentals of Software Defined Radio, and then show how low-level RFID communications could be considered in the same light. I will then go on to demonstrate the RFIDler prototype in action, reading, writing and emulating some common tags.