The flexibility of Software Defined Radio (SDR) technology has been employed to support various applications from the dynamic usage of the radio frequency spectrum to the implementation of various radio access technologies in the commercial and military domain. Very low-cost SDR devices have emerged in the last few years, opening new possibilities to implement inexpensive security attacks against radio protocols and systems. In this paper, we survey the state of art for the application of low-cost SDRs to the security domain and we describe a complete implementation of passive eavesdropping of DECT digital voice communications, where the DECT communication is not encrypted. The attack has been implemented with two different types of low-cost SDR platforms and the results are compared against various parameters. ; JRC.G.6-Digital Citizen Security