  The existence of an undetectable eavesdropping of dense coded information has
been already demonstrated by Pavi\v{c}i\'c for the quantum direct communication
based on the ping-pong paradigm. However, a) the explicit scheme of the circuit
is only given and no design rules are provided, b) the existence of losses is
implicitly assumed, c) the attack has been formulated against qubit based
protocol only and it is not clear whether it can be adapted to higher
dimensional systems. These deficiencies are removed in the presented
contribution. A new generic eavesdropping scheme built on a firm theoretical
background is proposed. In contrast to the previous approach, it does not refer
to the properties of the vacuum state, so it is fully consistent with the
absence of losses assumption. Moreover, the scheme applies to the communication
paradigm based on signal particles of any dimensionality. It is also shown that
some well known attacks are special cases of the proposed scheme.
