  We address continuous variable quantum key distribution (QKD) in
non-Markovian lossy channels and show how the non-Markovian features may be
exploited to enhance security and/or to detect the presence and the position of
an eavesdropper along the transmission line. In particular, we suggest a
coherent states QKD protocol which is secure against individual attacks for
arbitrarily low values of the overall transmission line. Our scheme relies on
specific non-Markovian properties, and cannot be implemented in ordinary
Markovian channels characterized by uniform losses.
