The Vrije Universiteit team found that compact malicious code could be written to RFID tags after all. By replacing a tag's normal identification code with a carefully written message, the researchers found they could exploit bugs in a computer connected to an RFID reader. This made it possible to spread a self-replicating computer worm capable of infecting other compatible, and rewritable, RFID tags.

Exploiting RFID Readers -- Viral RFID Prototype Created