"Although terrorist attacks and fatalities from terrorism declined globally for the second year in a row in 2016, terrorist groups continued to exploit ungoverned territory and ongoing conflict to expand their reach, and to direct and inspire attacks around the world. The Islamic State of Iraq and Syria (ISIS) remained the most potent terrorist threat to global security, with eight recognized branches and numerous undeclared networks operating beyond the group's core concentration in Iraq and Syria. Al-Qa'ida (AQ) and its regional affiliates remained a threat to the U.S. homeland and our interests abroad despite counterterrorism pressure by U.S. partners and increased international efforts to counter violent Islamist ideology and messaging. Terrorist groups supported by Iran -- most prominently Hizballah -- continued to threaten U.S. allies and interests even in the face of U.S.-led intensification of financial sanctions and law enforcement."
U.S. Department of State: http://www.state.gov/