I agree it is “certain” that al Qaeda intends to attack the U.S. homeland in the near future. It has the proven capability to pull off conventional attacks involving IEDs and suicide bombers, and such attacks have already occurred in Europe. We successfully foiled the 2006 liquid bomb plot and were lucky that Umar Abdulmutallab's weapon failed to detonate on Christmas Day. No doubt more attempts involving aircraft will occur, but I believe our ability to prevent and disrupt them is vastly improved.

• Daily Beast experts on how America can prepare for a terror attack The keys are sustained leadership by the Director of National Intelligence and a layered system of intelligence and detection that is nimble, flexible and constantly innovating against a sophisticated and ever-evolving threat. While 100 percent security is impossible, more must be done to manage the substantial risks we face.

Should an attack occur we must respond swiftly and unflinchingly, but be mindful that security and liberty are not a zero-sum game. That is why President Obama must act now to stand up the Privacy and Civil Liberties Oversight Board mandated by the 2004 Intelligence Reform Act —to ensure that we do not shred our Constitution in the process of defending our democracy.

Representative Jane Harman (D-California) chairs the intelligence subcommittee of the House Homeland Security Committee.