Traditionally, signals intelligence is neatly bifurcated into offense and defense: intercept adversaries’ communication technology and protect one’s own. In the modern era, however, there is great convergence in the technologies used by friendly nations and by hostile ones. Signals intelligence agencies find themselves penetrating the technologies they also at times must protect. To ease this tension, the United States and its partners have relied on an approach sometimes called Nobody But Us, or NOBUS: target communications mechanisms using unique methods accessible only to the United States. This approach, which calls for advanced methods, aims to protect communications from American adversaries, yet also ensure American access when needed. But it depends as well on a number of American advantages that are under serious threat. The decline of these advantages renews the tension between offense and defense once more. This paper examines how the NOBUS approach works, its limits, and the challenging matter of what comes next.