A panel of experts has said that naturalized Americans are a new possible threat to the United States. It is predicted that many will go overseas for training and experience and then return to conduct operations here. Currently this small group of people are called "foreign fighters". It is estimated that there are about three dozen Americans fighting with Jihadi groups in Waziristan, Pakistan. The panels product is a study called "Foreign Fighters: Trends, Trajectories & Conflict Zones". The document can be found on the Homeland Security Digital Library - an online library by the Naval Postgraduate School Center for Homeland Defense and Security - at the link below.