We suggest a sophisticated attack protocol, which can be applied to the two-way deterministic quantum key distribution protocol. When more than two photons are used for a qubit, Eve picks out a photon each from the forward and the backward channel and measures whether the states of the two picked-out photons are orthogonal or the same by using the fourth order quantum interference. We describe the attack protocol, which uses an active arrangement of two Hong-Ou-Mandel interferometers combined with further quantum nondemolition measurements, beam splitters, and polarization rotator. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.