Terrorism has become the most prominent security issue of the early 21st century and the response of western states to the threat POSED by terrorism has also been highly controversial. Terrorism has existed since 66AD with the sicarii in Palestine whose activities “would qualify them as terrorists”. This means terrorism is by no means a new thing. While terrorism’s origins may be easy to trace, the definition of terrorism is much more difficult to come to terms with as the pejorative nature of the word has resulted in no internationally agreed-upon legal definition. This problem is highlighted in Afghanistan where the United States of America supported the Islamist Mujahideen against the Soviet military in the 1980s, many of the leaders of these GROUPS then became leaders in the Taliban regime that the United States overthrew and is currently engaged in suppressing, resulting in a totally contradictory stance on the same terrorist group in the same location. There are also many types of security with traditional and new security having differing views on where the emphasis of security should LIE and what security actually is. This essay will first discuss what terrorism is including an attempt at a definition and the threat it poses, FOLLOWED by the discussion on what security is and how terrorism FITS into the many aspects of security today. It will be concluded that while terrorism does pose a threat to security there are more important security issues to be addressed.