The terrorist attacks of September 11 brought to a head change that had been underway since the end of the Cold War in how we think about security: (1) there is no longer consensus about who or what constitutes the “enemy”; (2) Realism as the dominating paradigm for studying international relations is collapsing; (3) domestic factors are gaining importance for devising security policies; and (4) with increasing globalization these domestic factors attain impact beyond national borders. In this article, I examine the nature of these developments and illustrate that the concept of security is often misapplied for political gain and/or to justify extraordinary measures for countering impending or perceived threats. Comparing various conceptions of security, I analyze the dangers resulting from oversecuritization, which is the propensity to treat traditional policy issues as existential threats to security, and demonstrate the need to more clearly define the distinction between nonexistential and existential threats that justify extraordinary measures. Expanding on classical security complex theory, I propose a conceptual model that links security sectors and can be applied to develop measurable criteria for distinguishing between those issues that should be securitized and those that can be addressed through existing policy channels.