Washington (CNN) - Another attempted terrorist attack on the United States in coming months is "certain," the heads of the major U.S intelligence agencies told a Senate committee Tuesday.
Al Qaeda remains the top security threat to the United States, but a growing cybersecurity threat also must be addressed by the U.S. intelligence community, the heads of the CIA, the FBI and other agencies told the Senate Intelligence Committee.
Asked by committee chair Sen. Dianne Feinstein of the likelihood of another attempted terror attack on the United States in the next three to six months, the officials agreed with Director of National Intelligence Dennis Blair's initial answer of "certain."
While none of the intelligence chiefs, who included CIA Director Leon Panetta, FBI Director Robert Mueller and others, cited a specific pending threat, their testimony made clear that an evolving al Qaeda remains their top concern.
"My greatest concern, and what keeps me awake at night, is that al Qaeda and its terrorist allies and affiliates could very well attack the United States," Panetta said. Al Qaeda is adapting methods to make their plots more difficult to detect, shifting from large attacks with multiple players to using individuals without any background in terrorism, Panetta said.
He noted the failed Christmas Day bombing of a U.S. airliner as an example, saying the suspect had a U.S. visa but little history of involvement with terrorist groups.
"Obviously, they decided to make use of someone like that within a very short period of time" of the suspect coming into contact with al Qaeda, Panetta said.