This week is the eleventh anniversary of the 9/11 attacks. Is their lasting legacy greater security for Americans from terrorist attacks because of everything the United States has done in their aftermath? Or, is it the erosion of our privacy and freedom?

Islamic terrorists have failed to launch another mass-destruction terrorist attack in the U.S. since 9/11. That’s largely because the U.S. military has killed so many al-Qaeda leaders in Iraq, Afghanistan, the Arabian Peninsula, and the Horn of Africa. The loss of al-Qaeda’s best and brightest in such large numbers has severely undercut its ability to plan and execute large scale terrorist attacks.

The life expectancy of an al-Qaeda leader has dropped from 54 to 40—Osama bin Laden’s and Anwar al-Awlaqi’s ages at death.

U.S. law enforcement, with two notable exceptions, also has prevented numerous Islamic-terrorist attempts to carry out lesser attacks in the US. In June 2009, at a recruiting office in Little Rock, Arkansas, Muslim convert Abdulhakim Mujahid Muhammad killed one U.S. Army private and wounded another. In November 2009, at Fort Hood Texas, U.S. Army Major Nidal Hassan killed 13 and wounded 32. The number of lives saved by preventing many other attacks is much greater.

Indeed, we are safer because of what brave, dedicated men and women have done to defend us. Nevertheless, Americans have paid a heavy price for this security; and it’s one, thus far, we have only made a down payment on.

The most obvious infringements on our privacy and freedom occur when we enter an airport to board a plane, where we are subjected to intrusive electronic and physical searches by Transportation Security Agency (TSA) screeners.

As embarrassing and humiliating as these searches often are, they are preferable to dying because a terrorist exploded a bomb on an aircraft; but is there a better way to protect the flying public that doesn’t subject them to such intrusive measures?

Less obvious are the proliferation of surveillance cameras, the monitoring of our communications, and the data mining of mass personal information by government that have increased exponentially since 9/11.

Today, 30 million surveillance cameras track our movements outside our homes. America’s streets, buildings, and parking lots are covered by them. Law enforcement agencies already have begun putting them in small, low-cost drones that can monitor us in our backyards.

The Patriot Act, initially passed on October 26, 2001, reduced restrictions in law enforcement agencies' gathering of intelligence within the U.S. and expanded the definition of terrorism to include domestic terrorism and other activities to which the Act’s law enforcement powers can be applied.

The Foreign Intelligence Surveillance Act (FISA), originally passed in 1978, was amended in 2001 by the Patriot Act, to include terrorism on behalf of groups that are not specifically backed by a foreign government. It provides warrantless access to all communications going between some of the nation's major telecommunication companies' and foreign locations, including phone conversations, email, web browsing, and corporate private network traffic.

The Cyber Intelligence Sharing and Protection Act (CISPA) is a proposed law which would allow for the sharing of Internet traffic information between the U.S. government and technology and manufacturing companies. The stated aim of the bill is to help the U.S government investigate cyber threats and ensure the security of networks against cyber-attack.

Data mining, the mass gathering of information on financial records, internet surfing habits, e-mail traffic and from social networks, is becoming an increasingly common tool of U.S. law enforcement and intelligence agencies. Made possible by the Internet and new technologies, simply by tracking the chip in your smartphone, the government can monitor your movements twenty-four-seven.

The chief criticism of these laws and activities is that they erode our civil liberties under our Constitution. They allow increased warrantless wiretaps of U.S. civilians, invade our privacy, and limit our freedom. New technologies such as facial recognition software, retinal scanning, and thermal facial analysis, already are in use and growing, will only further erode them.

Unlike screening at airports, because monitoring our movements and our communications isn’t obvious or physically intrusive, the majority of Americans aren’t overly concerned about them. They don’t become concerned until they receive speeding or red-light camera tickets in in the mail or until they wrongly show up on a no-fly list or become a “person of interest.”

Certainly, if we want to be safe from terrorist attacks, we have to accept tradeoffs. Physical security and surveillance are necessary evils of the age we live in. The problem with all this, however, is that government tends to go too far. No politician or government official wants to be the one who didn’t do enough to prevent a terrorist attack; so they error on the side of more security and surveillance and greater invasions of our privacy, even when, in the case of TSA screening at airports, it is highly inefficient and excessively intrusive. Profiling, a more effective technique is politically incorrect.

The lasting legacy of 9/11 is that we are safer, albeit still not immune from terrorist attack. Whatever measure of safety we have achieved, however, we have paid for it with intrusions into our privacy and limits on our freedom. We will continue to pay for it indefinitely, and that may be the real legacy of 9/11.