SETI (the official search for extraterrestrial intelligence) still argues that they have not received any anomalous radio signals to suggest extraterrestrial life exists. Whether this is the truth or not, that is their official line. But perhaps extraterrestrials would find radio transmissions a very easy way to communicate even through secret frequencies.
The big question is how is the extraterrestrial civilizations contacting the Governments that possess nukes.
Some scientists and engineers believe the communications are taking place secretly at very special short-wavelength, high-frequency signals that occupy the electromagnetic spectrum above 190 THz in the infrared range. It is the optical wireless range that requires special devices and is normally out of reach of the public though in some countries no licensing is required.
The communication in many cases are electro-magnetically shielded and encrypted. There are researchers all around the world who are receiving such signals and are working on reverse engineering the shield as well as the encryption. It will not be long before someone comes out with complete details of these secret communication mechanisms.
It is not known if the shielding of communication is created by the extraterrestrials or by the countries involved in such communication. Very strange signals are being passed in that frequency range and are very difficult to detect.