We describe the scientific objectives, the design concept and the implementation of the Dust Flux Analyser (DFA) for the ESA Rosetta mission. DFA is designed to detect individual dust particles in order to study their physical and dynamical properties as a function of time and of orbital position, to monitor the spatial distribution of the dust production and correlate it with the nucleus emission sites and to analyse gas-dust interactions and the evolution of the coma. The instrument is composed of three detectors with a common electronic box. The Velocity Measurement System (VMS) will measure the velocity of the incoming dust particles and the dust detector (MOM), its momentum. A separate deposition system (DEP) composed of three quartz microbalances will monitor the cometary dust flux in three directions, DFA will be able to detect dust particles in the size range 5-1000 mu m and velocity range 0.1-150 m.s(-1). Required resources are a mass of 4.9 kg, a power of 3.6 W to 16.7 W and a telemetry of 50 to 512 kBits per hour depending upon the operating modes