An unknown unknown is unidentified information. An individual or organization may realize that such information exists and is relevant to them but its specifics are completely outside of their scope of awareness. The term is one of four categories of information, which also includes known knowns, unknown knowns and known unknowns.
Unknown unknowns are pertinent to many areas of information technology, including big data, text mining, project management, software design and cybersecurity. In the context of big data, for example, an unknown unknown may represent an unidentified asset. Many organizations access and store huge volumes of unstructured data without much knowledge of its potential value. However, big data analytics software may identify patterns and connections among data that yield useful information.
In project management and security, on the other hand, unknown unknowns are more often spoken of as unidentified risks. Nevertheless, there is benefit in understanding that there may be completely unpredictable events and outcomes that could have a significant effect on an organization, and reserving some contingency resources to respond to such situations.
Current discussion about unknown unknowns and its variations arose from then-United States Secretary of Defense Donald Rumsfeld’s 2002 comment at a Defence Department briefing:
“There are known knowns. There are things we know that we know. There are known unknowns. That is to say, there are things that we now know we don't know. But there are also unknown unknowns. There are things we do not know we don't know.”
Rumsfeld was differentiating categories of knowledge in a military context. The comment was generally considered nonsensical and public response was derisive. Since then, however, the terms have been elaborated upon and applied in business, the sciences and other areas of endeavor.