"Over the last two years, European governments and the European Union (EU) have grown increasingly alarmed by the rise of the Islamic State terrorist organization, its ability to attract European citizens to join the fighting in the Syria-Iraq region, and its use of violent extremist propaganda to inspire others. Security experts view the November 13, 2015, attacks in Paris (which killed 130 people) and the March 22, 2016, bombings in Brussels (in which 32 people died) as indications that the Islamic State's capacity to direct large-scale, coordinated attacks elsewhere in the world, especially in Europe, has increased. Many of those identified as directly responsible for the Paris and Brussels attacks reportedly fought in Syria and were connected to a 'European Branch' of the Islamic State. Some observers suggest that there could be many potential European recruits among the estimated 5,000 Europeans who have traveled to Syria and Iraq to join the Islamic State and other extremist groups. […] European governments have employed various measures to combat Islamist terrorism and the foreign fighter phenomenon, including increasing surveillance, prohibiting travel, and arresting returning fighters and terrorism recruiters. Some countries have bolstered existing counterterrorism laws, especially to ensure that individuals who travel abroad for terrorist purposes may be prosecuted (as required by U.N. Security Council Resolution 2178 of September 2014). European officials are also working to more aggressively counter radicalization and extremist propaganda, especially via the Internet and social media. Some have called on U.S. technology companies to assist these efforts by preemptively removing terrorist content from their sites."
CRS Insight, IN10209
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html