Confronting the Terrorist Threat to the Homeland: Six Years After 9/11, Hearing Before the Committee on Homeland Security and Governmental Affairs, United States Senate, One Hundred Tenth Congress, First Session, September 10, 2007 [open pdf - 6MB]
From the testimony of Michael Chertoff: "The fact that we have not suffered another terrorist attack on our soil in the last 6 years does say something about the success of our efforts so far. Now, some people do say it is just because we are plain lucky. I do not believe ''luck'' is an adequate explanation for this. Others may contend that the terrorist threat has subsided or that the United States is no longer in danger, or maybe that the terrorists have lost interest. But, again, I would just commend the videotape we saw over the weekend as a refutation of that. I commend to you the arrests that we saw in Germany and Denmark. The enemy is very focused on continuing to wage this war. They have not lost interest, and if we allow ourselves to become complacent and to think that the threat has diminished, we are going to be crippling ourselves in our ability to prevent future attacks. It is not the case that the enemy has not tried to attack us over the past several years. In December 2001, the Shoe Bomber tried to blow up an airliner coming to the United States. Last summer the British, with our help, disrupted a plot that, had it been carried out, would have resulted in multiple explosions on airliners flying from the United Kingdom to the United States. So it is not for want of trying that we have not suffered a successful attack." Statements, letters, and materials submitted for the record include those of the following: J. Michael McConnell, John Scott Redd, and Robert S. Mueller.
S. Hrg. 110-893; Senate Hearing 110-893
Government Printing Office, Congressional Hearings: http://www.gpoaccess.gov/chearings/index.html