Security by design is a celebrated slogan that has been embraced by computer security practitioners. In this talk we will dive into the origins of this slogan in the 1970s, the implications for practitioners that face evolving threats, when systems that have been secure by design using decade-old criteria turn out to have insufficient protection. We will look into why formal methods are important for reasoning about negative properties (which security is) and how programming languages in particular can help enforce security properties, with concrete examples of mitigating traffic analysis. Finally, we will discuss the relevance of the slogan in the era of largely untrusted code.