  We introduce local filters as a means to detect the entanglement of bound
entangled states which do not yield to detection by witnesses based on positive
(P) maps which are not completely positive (CP). We demonstrate how such
non-detectable bound entangled states can be locally filtered into detectable
bound entangled states. Specifically, we show that a bound entangled state in
the orthogonal complement of the unextendible product bases (UPB), can be
locally filtered into a another bound entangled state that is detectable by the
Choi map. We reinterpret these filters as local measurements on locally
extended Hilbert spaces. We give explicit constructions of a measurement-based
implementation of these filters for $2 \otimes 2$ and $3 \otimes 3$ systems.
This provides us with a physical mechanism to implement such local filters.
