It's who they wrote to and when, and so forth. But it's been argued, and someone here in the audience has talked to a former NSA analyst who said metadata is actually much more invasive than the core data, because in the core data you present yourself as you want to be presented.
Se trata de a quién escribieron, cuándo, etc. Pero se ha esgrimido, alguien aquí en la audiencia ha dicho, un ex-analista de la NSA que dijo los metadatos son mucho más invasivos que los datos puros, porque en los datos puros uno se presenta como quiere presentarse.