More than nine years after the Sept. 11, 2001 terrorist attacks, the United States is still under "constant" threat, according to Attorney General Eric Holder.
Holder issued a warning to Americans in an interview today, saying that even though the U.S. continues to thwart potential threats, "the terrorists only have to be successful once."
Since Sept. 11, sweeping changes have been made to national security, including the formation of the Department of Homeland Security and broad procedural changes at the nation's airports.
But Holder said one of his greatest concerns was now the number of Americans who seem willing to kill their fellow citizens.
"It is one of the things that keeps me up at night," Holder said. "You didn't worry about this even two years ago -- about individuals, about Americans, to the extent that we now do. And -- that is of -- of great concern."
We want to know what you think: Are we any safer from the threat of terror than we were nine years ago?