In an op-ed column for USA Today Wednesday, Napolitano said, "our defenses should never have allowed this individual to board a plane bound for the United States.
On Tuesday, President Barack Obama told reporters intelligence agencies failed to connect the dots with Umar Farouk Abdulmutallab, the Nigerian man accused of trying to blow up a Northwest flight from Amsterdam to Detroit.
CBS News reported Tuesday that as early as August of 2009 the Central Intelligence Agency was picking up information on a person of interest dubbed "The Nigerian," suspected of meeting with "terrorist elements" in Yemen.
Sources tell CBS News "The Nigerian" has now turned out to be Abdulmutallab. But that connection was not made when Abudulmutallab's father went to the U.S. Embassy in Nigeria three months later, on November 19, 2009. It was then he expressed deep concerns to a CIA officer about his son's ties to extremists in Yemen, a hotbed of al Qaeda activity.
Napolitano said that preventing future attacks will require "multiple layers of defense," composed of federal, state and local law enforcement in addition to gathering intelligence abroad.
The secretary adds: "This is a shared responsibility in which we all have a role to play — from the traveling public alerting authorities when they see something suspicious to federal agencies working together to piece together clues to foil potential plots."
More coverage from CBSNews.com:
Abdulmutallab's Missing Months in Yemen
U.S. Intel Lapses Helped Abdulmutallab
Obama: "Systemic Failure" Allowed Attack
TSA Still Vexed by Explosives Screening
Did Abdulmutallab Talk to Radical Cleric?
Growing Al Qaeda Threat from Yemen
Abdulmutallab Lonely, Web Postings Suggest
Confusion Reigns Over Flight Security
Christmas Incident Renews Scanner Debate
Abdulmutallab's "Jihad Fantasies" Revealed
Behind the Abdulmutallab Security Breach
What Lies Ahead for Air Travel
Al Qaeda: We Planned Flight 253 Bombing
Obama: Plane Bomb Plot a "Serious Reminder"
Expert: New Security Steps a Smokescreen