Islamist militants controlling parts of Iraq and Syria have purportedly released a new audio recording warning Americans that "you will not feel secure even in your bedrooms."
9/11 commission issues new recommendations for preventing future terrorist attacks. Jay Gray reports.
Authorities now say a sniper was behind an April attack of 17 electrical transformers in Southern California. They're now treating the incident as a terror attack.
Canadian authorities have broken up what is being described as a "major terrorist attack" that may have included targets there and in New York.
The Energy Department has been hit by a major cyber-attack.
FBI agents arrest men accused of plotting to train terrorists overseas for future attacks in America.
11 years after losing her father in the 9/11 attacks, Caitlin Leavey works to help others heal. Erika Tarantal reports.
The CIA foiled a plot by al-Qaida's affiliate in Yemen to bomb a U.S.-bound airliner around the one-year anniversary of the killing of its former leader Osama bin Laden, senior U.S. officials told NBC News.