It has been recently suggested that if the Extended Mind thesis is true, mental privacy might be under serious threat. In this paper, I look into the details of this claim and propose that one way of dealing with this emerging threat requires that data ontology be enriched with an additional kind of data—viz., mental data. I explore how mental data relates to both data and metadata and suggest that, arguably, and by contrast with these existing categories of informational content, (...) mental data should not be merely legally protected. Rather, if we value mental privacy as we know it, technological measures should be employed to ensure that one’s mental data are practically—not just legally—impossible for others to obtain. (shrink)