The Technology and Techniques Behind TSA’s Airport Security
Written by Calvin Drake
Biography
Calvin Drake is a Junior at USC who studies Interactive Media, which can be more
simply put as video game design. Drake has a deep fascination with systems, technology, and
security that drives him to constantly analyze and research new security technologies, in both
airports and other places like private businesses.
Abstract
Since 2008 the Transportation Security Administration (TSA) has been using full body
scanning machines to process passengers and eliminate the risk of non-metallic weapons being
brought onto planes, as well as to combat the increasing number of passengers trying to sneak
weapons by security. While these machines are imperfect and incapable of detecting some
dangerous materials such as explosives, they are an improvement over the metal detectors that
used to be used, and could be augmented with other security measures such as the inclusion of
bomb-sniffing dogs at security checkpoints to create a comprehensive security scan. Better
devices aren’t the only way that airport security can improve, though, as efforts in
mathematically optimizing efficiency for airports across the United States can speed up
processing time and ensure that resources are distributed to the airports that need them.
Keywords
Airport, Security, TSA, Scanner, Terrorism, Safety
Suggestions for Multimedia
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A three-panel comic showing the scanner sending out millimeter waves, them reflecting
back and being read by the machine, and an image being generated that identifies
potential threats could replace Fig. 1.
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A short, possibly looping animation for the “processing trouble” section that shows 2
different distributions of machines across a few airports – one distribution is balanced
and each airport finishes processing passengers at the same time, whereas one is
imbalanced and one airport finishes very quickly while others are left with long lines.
Introduction
In 2013 alone 1477 loaded firearms were discovered at Transportation Security
Administration (TSA) checkpoints in airports across the country, along with multiple incidents
of passengers attempting to bring pounds of black powder onboard [1]. While the TSA may be
criticized as being “security theater,” and seems like nothing more than an annoying hassle to
many, upon closer inspection its recent track record shows otherwise. These successes didn’t
come through raw human labor though, rather they relied on specially engineered devices to
search for contraband items, as well as various security practices and algorithms that best apply
the TSA’s limited resources and time to maximize security while also minimizing passenger
hassle.
Rising threat
Indeed, over the recent years the number of threats detected by the TSA have gone up –
and not by any small amount either – the TSA blog itself reports that from 2012 to 2013 there
was a 16.5% increase in the number of guns found on passengers or in their luggage [1].
Whether this is explained by better security devices and practices being able to detect more, or
by the sheer number of people attempting to bring contraband items onto airplanes, or both, is
difficult to tell because there’s no real clear statistic on the number of passengers that slip by
undetected. Speaking about the seemingly insanely high detection rate, TSA spokesman David
Castelveter remarks that the “TSA doesn’t believe these gun-toting passengers are terrorists” [2].
It would, of course be rather ridiculous for there to be multiple hijacking attempts every single
day – however with the stakes so high the TSA can’t afford to not treat every case of attempted
smuggling with the utmost severity until the passenger is proven harmless. This leaves the TSA
to both detect all of these attempts to bring a gun onboard, determine whether the passenger is a
terrorist or a law abiding citizen, and punish them accordingly, all while maintaining a smooth
and effective security process for all other passengers that must pass through security. Despite
this task being gargantuan, all of these failed attempts to bring guns onboard can also highlight
the ability for the TSA to utilize new and innovative engineering to discover hidden weapons –
some being hidden away in baggage linings or amongst other items to attempt to mask their xray signature, or cleverly disguised on passengers’ persons.
Comprehensive scan
Since 2008 full-body scanners have been used in airports to improve security and give
officers a clearer picture as to the nature of any object a passenger may try to carry on board with
them. Whereas the previously used metal detectors sent out pulses of magnetic energy and then
analyzed them, setting off an alarm if they were disturbed by a metallic object, but giving no
indication as to the nature, position, or size of the object, these full body scanners are much more
sophisticated. The machine rotates a combination projector and receiver around a passenger’s
body vertically and scans the passenger by sending out a pulse of weak radiation (either in the
form of millimeter waves or x-rays), and then looking at what gets reflected off the passenger’s
body. These machines allow TSA officials to actually view an image that represents the shape
and density of everything scanned. (See Fig. 1)
Basic workings of a millimeter-wave imaging machine
Fig. 1 – This machine is able to simultaneously read distance and density of both sides
of the passenger, creating a 3d image that can highlight potential threats
Source: http://www.scientificamerican.com/media/inline/A9678DB5-B0F2-0644-200F49C163148E01_1.jpg
Low density items, such as clothing, don’t show up on the scan at all, medium density
items such as the human body show up as shades of white and gray, and high density items show
up as pure black. The immediate benefit of these machines is the ability to detect non-metallic
items, such as ceramic knives or plastic guns.
Ceramic Threat
These threats aren’t just theoretical, either. Multiple non-metallic blades have already
been stopped at TSA checkpoints by utilizing the full-body scanners [1]. Needless to say, such
blades would not have triggered metal detectors. More concerning than ceramic knives, however,
are the potential for plastic, 3d printed firearms to be smuggled past old metal detectors.
Although these weapons are illegal to own, they needn’t be bought on the black market, as
anyone with access to a 3d printer could print one in a matter of hours – the plans are free online.
Despite paling in comparison to a legitimate firearms due to only being able to fire one, preloaded shot, plastic guns are still fully capable of being deadly with that one shot [3]. These guns
and knives show the clear necessity for advanced imaging technologies in order to stay ahead of
the curve of specialty-made weapons intended to sneak past previous security measures.
Imperfect Data
These machines are far from perfect, however. According to a 2010 Time World article,
due to the nature of the machines being a density scan they “cannot detect low-density materials
such as powders, liquids, thin panes of plastic or anything that resembles skin” [4]. Because the
machines work by essentially scanning for density, they’re excellent at detecting hard or metal
objects, like knives or guns, which are much more dense than the human skin, however they’re
similarly terrible at detecting fluids, powders, or gels, all of which are potentially explosive, and
all share similar densities with human flesh – making them look like extra bits of fat to the
scanners. Because of these flaws these machines were heavily criticized when they made their
debut in 2008, with their opponents criticizing the increased privacy invasion in order to gain
only mildly increased security. However, despite the initial uproar in 2008, an independent
survey of 377 Thanksgiving eve travelers conducted by Agyemang Frimpong just two years later
showed that a massive 84% of these passengers actually stated that they “supported federal
government investigating possible terrorist threats even if it invaded their privacy” [5]. Despite a
majority of acceptance for security, the TSA has still been working to remove these privacy
concerns. A CNN article in June of 2013 reports that the TSA fully solved the concerns by
removing all full body scanners that did not receive a software update from their manufacturer to
automatically detect threats. This seemingly small software update is actually an important
engineering feature that uses image-recognition technology to allow the computer to identify
potential hidden objects and display their locations on a generic human body, removing the
previous necessity of having a human view the nude scans of passengers [6]. (See Fig. 2)
Software automatically detects and identifies potential threats
Fig. 2 – The scanner’s programming will display yellow boxes on areas of concern,
allowing officers to pat down only what areas are absolutely necessary.
Source: http://www.cnn.com/video/bestoftv/2011/07/20/exp.tsr.todd.tsa.body.scans.cnn.640x360.jpg
With this major privacy concern eliminated by smart object-detection programming, full body
scanners have no real disadvantages when compared to metal detectors. While they admittedly
still can’t detect explosives, they’re still upping the bar for overall security and this one flaw can
be covered by other security methods, such as employing bomb-sniffing dogs in security lines.
Processing Trouble
With greater security and more pat-downs for false positives comes greater processing
time per passenger, and with an average of over 1,700,000 passengers processed daily, [1] even
small increases in processing time add up quickly to create long, sprawling security lines that
require passengers to show up earlier and wait longer just to make it to their terminal. With not
enough time, scanners, or officers to scrupulously inspect every single passenger, the TSA is
forced to, in real time, split passengers into different “threat classes” depending on how likely
the TSA thinks they are to be a risk to the safety of their flight. Indeed, the problem of proper
resource allocation on such a massive scale with the added complication of having to factor in
human behavior all calls for some complex mathematics, such as those of Sewell, Lee, and
Jacobson, a trio with skills in statistics, optimization, and mathematics. In their 2013 paper,
Optimal allocation of aviation security screening devices, they address the complex issue by
using mathematical equations that take into account such variables as the reliability of any given
machine or system, the costs of false alarms, and quantifying perceived risk of passengers in
order to come to conclusions such as what machines should be purchased, where they should be
deployed, and who should be screened with what level of security [7]. Complex statistical
equations like this can put all the engineering that goes into the complex security devices
deployed at checkpoints to their best effect, and can drive the implementation of advanced
security procedures that can pinpoint low risk passengers to spend less resources scanning,
hopefully alleviating long security lines and creating bearable passenger security experiences for
everyone involved.
Conclusion
Since its inception, the TSA has been responsible for airline security in the United States,
and carries the heavy burden of simultaneously enforcing strict security to ensure the safety of its
passengers and also doing so in a timely manner to allow smooth passenger traffic through the
airport. Such a challenge requires not just TSA officers in the airports screening passengers, but
a significant amount of engineering to create complex devices that will automate the screening
process. The most recent of these devices is the full body scanner, which simultaneously
increases the officers’ capabilities to discover potential hidden threats as well as speeding up the
overall speed at which passengers can move through checkpoints. Devices alone cannot
maximize throughput, though, as work in mathematics and statistics must also be done to ensure
proper distribution of devices and workers to allow every single public airport across the United
States to screen its passengers in a thorough, but also rapid manner. While these various methods
do an excellent job with a proven track record of success in discovering potential threats, there is
always room for improvement. The widespread implementation of bomb-sniffing dogs could
help cover up the full body scanners’ inability to detect explosives, and additional optimization
in the way the TSA classifies passengers’ potential threat level could allow for less security
resources to be expended on lower risk passengers, allowing the TSA to get the most security for
their buck. However, even with this room for improvement, with no successful airplane attacks
to date coming out of United States airports since 9/11, it’s safe to say that the TSA seems to
have its passengers in good hands.
References
[1] B. Burns. (2014, Jan. 24) TSA Blog Year in Review: 2013 [Online]. Available:
http://blog.tsa.gov/
[2] J. Lowy. (2013, Jul. 05) TSA: More Fliers Arriving at Checkpoints with Guns
[Online]. Available: http://www.usatoday.com
[3] C. Johnson. (2013, Nov. 14) Plastic Guns Made With 3-D Printers Pose New Security
Concerns [Online]. Available: www.npr.org
[4] L. Cendrowicz (2010, Jan. 05) Can Airport Body Scanners Stop Terrorist Attacks
[Online]. Available: www.time.com
[5] A. Frimpong (2011, April 01) “Introduction of full body image scanners at the
airports: a delicate balance of protecting privacy and ensuring national
security” Journal of Transportation Security [Online]. Pp 221-229. Available:
http://link.springer.com/ [Mar. 1, 2014]
[6] M. M. Ahlers (2013, May 30) TSA removes body scanners criticized as too revealing
[Online]. Available: www.cnn.com
[7] E. C. Sewell et al (2013, Jan. 29) “Optimal allocation of aviation security screening
devices” Journal of Transportation Security [Online]. Pp 103-116. Available:
http://link.springer.com/ [Mar. 1, 2014]