Many tips and information received by legitimate sources have led to the arrests of terrorists. Although the Defense Department has a major role to play in the war on terrorism, we are not a domestic law enforcement agency, so we ask that you provide your information to the appropriate authorities, as shown below:

FBI: https://tips.fbi.gov/

Department of Homeland Security: 
http://www.dhs.gov/how-do-i/report-suspicious-activity

http://www.us-cert.gov/