"A British man sentenced to four years in jail in Dubai after cannabis weighing less than a grain of sugar was found embedded in the tread of his shoe has reportedly been pardoned ... The 43-year-old was arrested in September [2008] at Dubai International Airport ... Customs officers found 0.003 grams (0.0001 ounces) of cannabis in a cigarette stub stuck on the sole of one his shoes."

-- Sky News

When I read that I wondered how on earth Dubai customs found the traveller's "stash." I mean, just think about it; thousands of people passing through customs every day and the officials can spot something that tiny on the sole of his shoe! There has to be some kind of logical explanation.

Before I go any further, I must explain that the United Arab Emirates (the UAE), while considered perhaps the most liberal of the Arab Gulf states, is fanatically (and irrationally) anti-drug to the point where entering the country with melatonin tablets (an over-the-counter medication used to counter jet lag) or traces in your bloodstream of a whole list of chemicals will get you arrested!

Want crazier? It was reported in 2008 that a Swiss national went to jail for four years in the UAE when customs found -- and I'm not kidding -- three poppy seeds on his clothes from a bread roll he consumed at Heathrow.

Now, you're probably wondering how on earth could UAE customs detect 0.0001 ounces of cannabis or three poppy seeds? A 2008 BBC report quoted Fair Trials International's chief executive, Catherine Wolthuizen, who claimed that "authorities were using highly sensitive new equipment to conduct thorough searches on travelers."

I can't find any reports of exactly what kind of "highly sensitive" equipment was in use in the UAE in 2008, but I can tell you that by 2010 UAE customs was using full body scanners.

There are two types of full body scanners: Backscatter X-ray scanners and millimeter wave scanners.

Backscatter X-ray scanners "bounce" X-rays off people and questions about the safety of these devices still remain unanswered (you can buy [radiation shielding underwear][http://www.rockyflatsgear.com/] if you're worried or shy).

Millimeter wave scanners (which are, apparently considered safe) operate in the sub-terahertz band (non-ionizing radiation with a wavelength greater than one millimeter) and are either passive (which detect natural millimeter radiation) or active (which "bathes" the target in generated millimeter radiation).

How good are these systems? Apparently not very good as both types of scanner have a limited ability to "see" through multiple layers of clothing and can't examine body cavities.

According to a Wired article from 2011: "A study published in the November edition of the Journal of Transportation Security suggested terrorists might fool the Rapiscan machines and others like it employing the X-ray "backscatter" technique. A terrorist, the report found, could tape a thin film of explosives of about 15-20 centimeters in diameter to the stomach and walk through the machine undetected."

TSA surveillance: Peep show, police state, privacy invasion or all three?

Add to that the issue that the scanners produce what is, at best, a poor quality but recognizable "nude" image of the person scanned, and you have to wonder how the UAE customs detected specks of weed and a few poppy seeds.

The true answer was probably more to do with social engineering and expert observation of passengers than technology. UAE customs officers have very frequent and visible patrols in Dubai airport to make those engaged in illicit activities nervous and a ridiculous number of security cameras manned, presumably, by a ridiculous number of officers, continuously watching the crowds.

But today, I suspect that UAE customs have upped their game because what they are most likely now using are terahertz scanners.

Terahertz scanners use terahertz radiation which is interesting stuff. Wikipedia explains:

Terahertz radiation falls in between infrared radiation and microwave radiation in the electromagnetic spectrum, and it shares some properties with each of these. Like infrared and microwave radiation, terahertz radiation travels in a line of sight and is non-ionizing. Like microwave radiation, terahertz radiation can penetrate a wide variety of non-conducting materials. Terahertz radiation can pass through clothing, paper, cardboard, wood, masonry, plastic and ceramics. The penetration depth is typically less than that of microwave radiation. Terahertz radiation has limited penetration through fog and clouds and cannot penetrate liquid water or metal.

Of great relevance to enterprise networking folks:

In May 2012, a team of researchers from the Tokyo Institute of Technology published in Electronics Letters that it had set a new record for wireless data transmission by using T-rays and proposed they be used as bandwidth for data transmission in the future. The team's proof of concept device used a resonant tunneling diode (RTD) [and] sent a signal at 542 GHz, resulting in a data transfer rate of 3Gbps. The demonstration was 20 times faster than the current Wi-Fi standard and doubled the record for data transmission set the previous November. The study suggested that Wi-Fi using the system would be limited to approximately 10 metres (33 feet), but could allow data transmission at up to 100Gbps.

Would that be fast enough wireless for you?

Anyway, one of the many interesting aspects of terahertz radiation is something called "terahertz spectroscopy". One of the leading vendors in terahertz technology, Genia Photonics, offers products in this area and explains:

Sensing science and technology of explosives and related compounds (ERC) are crucial for homeland security and defense-related applications. A wide variety of detection methods are involved in explosive detection including X-rays, infrared, THz, microwave, gamma-rays, etc. The field of terahertz (THz) spectroscopy has been investigated many times over previous years as a technique for the detection of explosive vapour signatures. THz waves can penetrate through many dielectric materials, such as clothing, paper, plastics, leather, wood and ceramics. In addition, THz radiation has low photon energies and will not cause harmful photoionization in biological tissues. Owing to these advantages, THz technology is a competitive method for inspecting explosives carried by a person or concealed in packages. Terahertz radiation lies in the far infrared region from 0.1 to 10 THz. Most explosives and explosive-related compounds have spectral fingerprints within this range and, as many apparatus operate within the range 0.1-5.0 THz.

So, terahertz radiation scanning can detect explosives and, according to [a paper on the Genia site][http://www.geniaphotonics.com/publications/technical-notes/2012/01/multiphoton-spectroscopy/download/], "pharmacological substances" as well.

But wait! It gets better! This detection doesn't require the person or thing being examined to be in an enclosure or even to be close! The system works by having a terahertz laser generate a pulse from up to around 150 feet away and the reflected radiation will contain "molecular signatures" that can be decoded, so it is claimed, in picoseconds! And this includes signatures of substances in your bloods stream! And the entire system is in what looks like a 3U rack-mounted enclosure!

So, you could have one of these systems pointing down a hallway and scanning every person who walks past in real time! Speck of weed on Bob's shoe? Nailed! Poppy seeds in Ann's pocket? Got her! Vicodin in Dave's briefcase? Wham! Cherry Bomb in Harry's lunch box? Take him down!

If these devices work as proposed, scanning of anyone and everyone anywhere will become commonplace. Forget drug testing in business environments ... you'll just be scanned as you enter. If you have drugs or just their residues on you, or if the metabolites are in your blood stream, they will, it is claimed, be detected.

I wonder whether a more sophisticated computer analysis of terahertz scanning data will allow for the identification of individuals through their own unique combination of molecular signatures?

And then there's the implications for the "War on Drugs" that the U.S. has been expensively (we spent $18.4 billion in 2000 of which only 1% went to prevention, treatment, and research) waging since 1914 (it was Nixon who coined the phrase "War on Drugs," but it was the Harrison Narcotics Tax Act that set the eight ball in motion). Terahertz scanning technology will potentially enable the most comprehensive and secretive wholesale drug screening of U.S. citizens that has ever been conceived! Go anywhere near any government offices and you could be scanned and categorized.

But what will happen to those traveling through Dubai airport? Don't, under any circumstances, go anywhere near any kind of drugs ... not even legal ones unless you have the doctor's prescriptions with you because they'll scan you as you step off the plane and you'll be under interrogation before you know it.

But wait! In 2009, when bank notes were tested for traces of cocaine, the drug was found on 90% of U.S. banknotes along with 85% of Canadian, 80% of Brazilian, 20% of Chinese, and 12% of Japanese. Given the enthusiasm with which the UAE tracks down and incarcerates people for drugs, you might not want to travel with paper money.

Oh, and don't forget to wipe your shoes. Very thoroughly. Hell, better buy a new pair of shoes just in case.

Gibbs, in Ventura, Calif., has no plans to travel to Dubair. Your itinerary to backspin@gibbs.com and follow him on Twitter (@quistuipater) and on Facebook (quistuipater).

Read more about data center in Network World's Data Center section.

This story, "Terahertz Scanners, Drugs, and Shoes" was originally published by Network World .