The ‘Search for Extra-Terrestial Intelligence’ (SETI) keeps trying to eavesdrop on ‘our’ (i.e. from the  alien viewpoint) conversations using ideas and approaches that really don’t have much chance of succeeding. The information and ideas we ‘transmit’ across the vast distances of inter-stellar space are extremely valuable both for their content, as well as, the expense of the transmission itself. Given that these ideas and information are also potentially dangerous to cultures and social systems without the neccessary trail of intellectual assimilation to properly context the information or idea in the ‘local’ society, any alien culture would go to great lengths to ‘hide’ or encrypt both the transmission method and the information transmitted.

Even with the current technology available on ‘Earth’, it is possible to use multiple transmission frequencies across the whole electromagnetic spectrum. Anyone sampling the whole electromagnetic spectrum for artificially produced signals would think they are receiving ‘noise’ without knowing exactly the transmisson methodology and the ‘coding’ schema involved. Even advanced alien civilizations already in contact with other aliens would need to have such systems in place to both protect their own cultures from disruptive ideas and technolgies, as well as, insure the safety and viability of information to be used in inter-galactic trade. Of course, this doesn’t take into account the possibility that there may be transmission methods that go technologically beyond systems like radio, television, light and lasers, or anything else currently being utilized on ‘Earth’.