In a humbly-toned USA Today opinion piece yesterday, Secretary of Homeland Security Janet Napolitano asked for the public's cooperation with airline security measures the Transportation Security Administration has recently implemented. The TSA has come up with an invasive pairing: "Advanced Imaging Technology," also known as "strip-search machines" and, for those refusing, "enhanced" pat-downs which explore areas of the body typically reserved for one's spouse or doctor.

Anecdotal reports suggest that the machines are being used to ogle women, and we are seeing disturbing images and videos of children being handled by strangers online. The public is increasingly agitated by the TSA's latest amendment to the air travel ordeal, and a "National Opt-Out Day" is slated for next Wednesday, the biggest travel day of the year.

Twice, Secretary Napolitano notes that these measures are "risk-based" or "driven by . . . risk." But has the Department of Homeland Security conducted the necessary risk management studies to validate these programs? A March 2010 Government Accountability Office report says:

[I]t remains unclear whether the AIT would have detected the weapon used in the December 2009 incident based on the preliminary information GAO has received. . . . In October 2009, GAO also recommended that TSA complete cost-benefit analyses for new passenger screening technologies. While TSA conducted a life-cycle cost estimate and an alternatives analysis for the AIT, it reported that it has not conducted a cost-benefit analysis of the original deployment strategy or the revised AIT deployment strategy, which proposes a more than twofold increase in the number of machines to be procured.

I've seen no documentation that the strip-search machines, the invasive pat-downs, or their combination have been subjected to any thorough risk analysis. The DHS has mouthed risk terminology for years now, but evidence is scant that it has ever subjected itself to such rigor.

Risk Management

A formal risk management effort will generally begin with an examination of the thing or process being protected. This is often called “asset characterization.” In airline security, the goal is fairly simple: ensuring that air passengers arrive safely at their destinations. Specifically, ensuring that nobody successfully brings down a plane.

The next step in risk management is to identify and assess risks, often called “risk characterization” or “risk assessment.” The vocabulary of risk assessment is not settled, but there are a few key concepts that go into it:

• Vulnerability is weakness or exposure that could prevent an objective from being reached. Vulnerabilities are common, and having a vulnerability does not damn an enterprise. The importance of vulnerabilities depend on other factors.
• Threat is some kind of actor or entity that might prevent an objective from being reached. When the threat is a conscious actor, we say that it “exploits” a vulnerability. When the threat is some environmental or physical force, it is often called a “hazard.” As with vulnerability, the existence of a threat is not significant in and of itself. A threat’s importance and contribution to risk turns on a number of factors.
• Likelihood is the chance that a vulnerability left open to a threat will materialize as an unwanted event or development that frustrates the safety, soundness, or security objective. Knowing the likelihood that a threat will materialize is part of what allows risk managers to apportion their responses.
• Consequence is the significance of loss or impediment to objectives should the threat materialize. Consequences can range from very low to very high. As with likelihood, gauging consequence allows risk managers to focus on the most significant risks.

Analyzing vulnerabilities and threats permits risk managers to make rough calculations about likelihood and consequence. This process will float the most significant risks to the surface. Though these factors are often difficult to measure, a simple formula guides risk assessment:

Likelihood x Consequence = Risk

Events with a high likelihood and consequence should be addressed first, and with the most assets. Those are the highest risks.

The most common error I see in risk management is the propensity to attack vulnerabilities rather than risks. A bomber's attempt to take down a plane by concealing explosives in his undergarments last year exposed a vulnerability. It is possible to sneak a small quantity of explosive through conventional security systems, though not necessarily the needed detonator and not necessarily enough explosive material to take down a plane.

But this says nothing about the likelihood of this happening again---or of being successful. In hundreds of millions of enplanements each year, this attack has manifested itself once. And it failed. The TSA effort is going after a vulnerability---of that there is no doubt---but it is arguable whether or not it is addressing a significant risk.

After risk assessment, the next step in risk management is choosing responses.

Though the concepts and terminology are not settled in this area either, there are four general ways to respond to risk:

• Acceptance – Acceptance of a threat is a rational alternative that is often chosen when the threat has low probability, low consequence, or both.
• Prevention – Prevention is the alteration of the target or its circumstances to diminish the risk of the bad thing happening.
• Interdiction – Interdiction is any confrontation with, or influence exerted on, a threat to eliminate or limit its movement toward causing harm.
• Mitigation – Mitigation is preparation so that, in the event of the bad thing happening, its consequences are reduced.

In its operation, the strip-search/grope combo is an interdiction against any who may try to carry dangerous articles on planes. As to the air transportation system, it might also be conceived of as a preventive measure.

The next analytical lens to look through is benefit-cost analysis, or trade-offs. The goal is to allay risk in a cost-effective way, spending the least amount of money, and incurring the least costs overall, per unit of benefit.

Security Benefits

Security systems involve difficult and complex balancing among many different interests and values. The easiest, by far, is comparing the dollar costs of security measures against the dollar benefits. This is analysis that GAO says the TSA has not done.

But if it were done, on the benefit side of the equation, you have that it reveals most articles a person might try to sneak onto a plane. There are at least two important limitations on the benefit. First, there is an open question as to whether the strip-search machine would successfully detect lower-density material like the explosive PETN. If it doesn't, it's utility against underpants bombing relies on potential attackers' ignorance of that to deter their attempts. Second, the benefit of the strip-search/grope is not what it achieves from a basline of zero, but the marginal security improvement in provides over alternatives like the status quo magnetometer and random pat-downs.

How do you reduce security benefit to something measurable? It's difficult, but I've been mulling a methodology for valuing security against rare attacks in which you assume a motivated attacker that would eventually succeed. By approximating the amount of damage the attack might do and how long it would take to defeat the security measure, one can roughly estimate its value.

Say, for example, that a particular attack might cause one million dollars in damage. Delaying it for a year is worth $50,000 at a 5% interest rate. Delaying for a month an attack that would cause $10 billion in damage is worth about $42 million. It is best to assume that any major attack will happen only once, as it will produce responses that prevent it happening twice. (The 9/11 “commandeering” attack on air travel is an instructive example. By late morning on September 11, 2001, passengers and crew recognized that cooperation with hijackers contributed to the deadliness of attacks rather than saving their lives. They spontaneously changed the security practice to meet the new threat, and the 9/11 attacks permanently changed the posture of air passengers toward hijackers, along with hardened cockpit doors bringing the chance of another commandeering attack on air travel very close to nil.)

Of course, one must consider "risk transfer." That's the shifting of risks from one target to another---say, from planes to buildings. (An organization like the Department of Homeland Security would regard this as lowering the benefit of a security measure, while an airline would be indifferent to it---unless it owned the building...) There is also the creation of new risks, such as the possible health effects of the strip-search machines. Which brings us to the cost side of the ledger....

Costs

On the cost side of the ledger, the easy stuff to measure includes the hundreds of millions or billions of dollars that must be spent on strip-search machines themselves. As much or more money will be spent on an ongoing basis to operate the machines. My observation is that it takes three people to operate one strip-search machine: a guide, an analyst to review the image, and a person to do the secondary pat-down which occurs regularly (though it would occur less over time). On a nationwide scale, this is hundreds of millions of dollars per year spent on TSA employees.

The value of travelers' time is also important. This hasn't received much discussion, but as more and more strip-search machines come into use, there will be more discussion of how much time they consume compared to magnetometers.

Reviewing tape of TSA checkpoints reveals that passing through the machines takes at least seven seconds per passenger. Variations in the time it takes to traverse the security checkpoint require all travelers to increase the amount of time they spend at the airport as a cushion against the risk of missing flights, which can cost many hours per incident. If each of 350 million trips in a year results in an additional minute at the airport to accommodate the vagaries of the strip/grope, five to six million person hours at the airport will be wasted, a cost of $145 million per year if we value travelers' time at  $25 per hour.

It is more difficult is to balance interests like privacy and dignity against security benefits. A CBS News poll released yesterday says that four out of five Americans support the use of "'full-body' digital x-ray machines to electronically screen passengers."

It's an antiseptic description that strangely emphasizes computing. (X-rays are neither digital nor electronic, though the data the x-ray machines collect is digital and its processing is done with electronics.) The question doesn't capture people's feelings about images of their own denuded bodies being observed by a government official as a condition of travel. And, of course, it doesn't capture feelings about the intimate pat-down alternative.

The amount of public reporting and discussion suggests that public opinion is not solidly on the side of the strip/grope. A hearing in the Senate tomorrow is also evidence that the security procedures do not comport with the American people's rough judgment that the costs of these security measures are justified by their benefits.

My own view is that the strip/grope is security excess. If I had my way, I would choose the airlines and airports that do not go to this extreme. I do not get to have my way, and neither do you if you prefer a different security/privacy mix, because we all must use the same security system. That's why I wrote five years ago that the TSA should be abolished and responsibility for security restored to airlines and airports. Their experimentation could blend security with privacy, convenience, and comfort, improving the travel experience overall while restoring liberty to American travelers.