This chapter introduces natural language information assurance and security (NL IAS), a new front in information security effort enabled by applying the Ontological Semantics approach to natural language processing to the existing and new applications. It reviews the earlier (1999–2004) application implementations, their increasing and expanding computational semantic foun This chapter introduces natural language information assurance and security (NL IAS), a new front in information security effort enabled by applying the Ontological Semantics approach to natural language processing to the existing and new applications. It reviews the earlier (1999–2004) application implementations, their increasing and expanding computational semantic foundations, and new advances (2010–2013). The thrust of the chapter is that access to comprehensive natural language meaning—incrementally approximating human understanding and based on the dedicated semantic resources, the language independent property rich ontology, and language-specific lexicons—is necessary for the design and implementation of high precision applications in authenticating and protecting natural language files.