October 19, 2017

Archives for November 2008

Low Hit Rate Isn't the Problem with TSA Screening

The TSA, which oversees U.S. airport security, comes in for a lot of criticism — much of it deserved. But sometimes commentators let their dislike for the TSA get the better of them, and they offer critiques that don’t stand up logically.

A good example is yesterday’s USA Today article on TSA’s behavioral screening program, and the commentary that followed it. The TSA program trained screeners to look for nervous and suspicious behavior, and to subject travellers exhibiting such behavior to more stringent security measures such as pat-down searches or short interviews.

Commentators condemned the TSA program because fewer than 1% of the selected travellers were ultimately arrested. Is this a sensible objection? I think not, for reasons I’ll explain below.

Before I explain why, let’s take a minute to set aside our general opinions about the TSA. Forget the mandatory shoe removal and toiletry-container nitpicking. Forget that time the screener was rude to you. Forget the slippery answers to inconvenient Constitutional questions. Forget the hours you have spent waiting in line. Put on your blinders please, just for now. We’ll take them off later.

Now suppose that TSA head Kip Hawley came to you and asked you to submit voluntarily to a pat-down search the next time you travel. And suppose you knew, with complete certainty, that if you agreed to the search, this would magically give the TSA a 0.1% chance of stopping a deadly crime. You’d agree to the search, wouldn’t you? Any reasonable person would accept the search to save (by assumption) at least 0.001 lives. This hypothetical TSA program is reasonable, even though it only has a 0.1% arrest rate. (I’m assuming here that an attack would cost only one life. Attacks that killed more people would justify searches with an even smaller arrest rate.)

So the commentators’ critique is weak — but of course this doesn’t mean the TSA program should be seen as a success. The article says that the arrests the system generates are mostly for drug charges or carrying a false ID. Should a false-ID arrest be considered a success for the system? Certainly we don’t want to condone the use of false ID, but I’d bet most of these people are just trying to save money by flying on a ticket in another person’s name — which hardly makes them Public Enemy Number One. Is it really worth doing hundreds of searches to catch one such person? Are those searches really the best use of TSA screeners’ time? Probably not.

On the whole, I’m not sure I can say whether the behavioral screening program is a good idea. It apparently hasn’t caught any big fish yet, but it might have positive effects by deterring some serious crimes. We haven’t seen the data to support it, and we’ve learned to be skeptical of TSA claims that some security measure is necessary.

Now it’s time for the professor to call on one of the diehard civil libertarians in the class, who by this point are bouncing in their seats with both hands waving in the air. They’re dying to point out that our system, for good reason, doesn’t automatically accept claims by the authorities that searches or seizures are justified, and that our institutions are properly skeptical about expanding the scope of searches. They’re unhappy that the debate about this TSA program is happening after it was in place, rather than before it started. These are all good points.

The TSA’s behavioral screening is a rich topic for debate — but not because of its arrest rate.

Can Google Flu Trends Be Manipulated?

Last week researchers from Google and the Centers for Disease Control unveiled a cool new research result, showing that they could gauge the level of influenza infections in a region of the U.S. by seeing how often people in those regions did Google searches for certain terms related to the flu and flu symptoms. The search-based predictions correlate remarkably well with the medical data on flu rates — not everyone who searches for “cough medicine” has the flu, but enough do that an increase in flu cases correlates with an increase in searches for “cough medicine” and similar terms. The system is called Google Flu Trends.

Privacy groups have complained, but this use of search data seems benign — indeed, this level of flu detection requires only that search data be recorded per region, not per individual user. The legitimate privacy worry here is not about the flu project as it stands today but about other uses that Google or the government might find for search data later.

My concern today is whether Flu Trends can be manipulated. The system makes inferences from how people search, but people can change their search behavior. What if a person or a small group set out to convince Flu Trends that there was a flu outbreak this week?

An obvious approach would be for the conspirators to do lots of searches for likely flu-related terms, to inflate the count of flu-related searches. If all the searches came from a few computers, Flu Trends could presumably detect the anomalous pattern and the algorithm could reduce the influence of these few computers. Perhaps this is already being done; but I don’t think the research paper mentions it.

A more effective approach to spoofing Flu Trends would be to use a botnet — a large collection of hijacked computers — to send flu-related searches to Google from a larger number of computers. If the added searches were diffuse and well-randomized, they would be very hard to distinguish from legitimate searches, and the Flu Trends would probably be fooled.

This possibility is not discussed in the Flu Trends research paper. The paper conspicuously fails to identify any of the search terms that the system is looking for. Normally a paper would list the terms, or at least give examples, but none of the terms appear in the paper, and the Flu Trends web site gives only “flu” as an example search term. They might be withholding the search terms to make manipulation harder, but more likely they’re withholding the search terms for business reasons, perhaps because the terms have value in placing or selling ads.

Why would anyone want to manipulate Flu Trends? If flu rates affect the financial markets by moving the stock prices of certain drug or healthcare companies, then a manipulator can profit by sending false signals about flu rates.

The most interesting question about Flu Trends, though, is what other trends might be identifiable via search terms. Government might use similar methods to look for outbreaks of more virulent diseases, and businesses might look for cultural trends. In all of these cases, manipulation will be a risk.

There’s an interesting analogy to web linking behavior. When the web was young, people put links in their sites to point readers to other interesting sites. But when Google started inferring sites’ importance from their incoming links, manipulators started creating links for their Google-effect. The result was an ongoing cat-and-mouse game between search engines and manipulators. The more search behavior takes on commercial value, the more manipulators will want to change search behavior for commercial or cultural advantage.

Anything that is valuable to measure is probably, to someone, valuable to manipulate.

The future of photography

Several interesting things are happening in the wild world of digital photography as it’s colliding with digital video. Most notably, the new Canon 5D Mark II (roughly $2700) can record 1080p video and the new Nikon D90 (roughly $1000) can record 720p video. At the higher end, Red just announced some cameras that will ship next year that will be able to record full video (as fast as 120 frames per second in some cases) at far greater than HD resolutions (for $12K, you can record video at a staggering 6000×4000 pixels). You can configure a Red camera as a still camera or as a video camera.

Recently, well-known photographer Vincent Laforet (perhaps best known for his aerial photographs, such as “Me and My Human“) got his hands on a pre-production Canon 5D Mark II and filmed a “mock commercial” called “Reverie”, which shows off what the camera can do, particularly its see-in-the-dark low-light abilities. If you read Laforet’s blog, you’ll see that he’s quite excited, not just about the technical aspects of the camera, but about what this means to him as a professional photographer. Suddenly, he can leverage all of the expensive lenses that he already owns and capture professional-quality video “for free.” This has all kinds of ramifications for what it means to cover an event.

For example, at professional sporting events, video rights are entirely separate from the “normal” still photography rights given to the press. It’s now the case that every pro photographer is every bit as capable of capturing full resolution video as the TV crew covering the event. Will still photographers be contractually banned from using the video features of their cameras? Laforet investigated while he was shooting the Beijing Olympics:

Given that all of these rumours were going around quite a bit in Beijing [prior to the announcement of the Nikon D90 or Canon 5D Mark II] – I sat down with two very influential people who will each be involved at the next two Olympic Games. Given that NBC paid more than $900 million to acquire the U.S. Broadcasting rights to this past summer games, how would they feel about a still photographer showing up with a camera that can shoot HD video?

I got the following answer from the person who will be involved with Vancouver which I’ll paraphrase: Still photographers will be allowed in the venues with whatever camera they chose, and shoot whatever they want – shooting video in it of itself, is not a problem. HOWEVER – if the video is EVER published – the lawsuits will inevitably be filed, and credentials revoked etc.

This to me seems like the reasonable thing to do – and the correct approach. But the person I spoke with who will be involved in the London 2012 Olympic Games had a different view, again I paraphrase: “Those cameras will have to be banned. Period. They will never be allowed into any Olympic venue” because the broadcasters would have a COW if they did. And while I think this is not the best approach – I think it might unfortunately be the most realistic. Do you really think that the TV producers and rights-owners will “trust” photographers not to broadcast anything they’ve paid so much for. Unlikely.

Let’s do a thought experiment. Red’s forthcoming “Scarlet FF35 Mysterium Monstro” will happily capture 6000×4000 pixels at 30 frames per second. If you multiply that out, assuming 8 bits per pixel (after modest compression), you’re left with the somewhat staggering data rate of 720MB/s (i.e., 2.6TB/hour). Assuming you’re recording that to the latest 1.5TB hard drives, that means you’re swapping media every 30 minutes (or you’re tethered to a RAID box of some sort). Sure, your camera now weighs more and you’re carrying around a bunch of hard drives (still lost in the noise relative to the weight that a sports photographer hauls around in those long telephoto lenses), but you manage to completely eliminate the “oops, I missed the shot” issue that dogs any photographer. Instead, the “shoot” button evolves into more of a bookmarking function. “Yeah, I think something interesting happened around here.” It’s easy to see photo editors getting excited by this. Assuming you’ve got access to multiple photographers operating from different angles, you can now capture multiple views of the same event at the same time. With all of that data, synchronized and registered, you could even do 3D reconstructions (made famous/infamous by the “bullet time” videos used in the Matrix films or the Gap’s Khaki Swing commercial). Does the local newspaper have the rights to do that to an NFL game or not?

Of course, this sort of technology is going to trickle down to gear that mere mortals can afford. Rather than capturing every frame, maybe you now only keep a buffer of the last ten seconds or so, and when you press the “shoot” button, you get to capture the immediate past as well as the present. Assuming you’ve got a sensor that let’s you change the exposure on the fly, you can also now imagine a camera capturing a rapid succession of images at different exposures. That means no more worries about whether you over or under-exposed your image. In fact, the camera could just glue all the images together into a high-dynamic-range (HDR) image, which yields sometimes fantastic results.

One would expect, in the cutthroat world of consumer electronics, that competition would bring features like this to market as fast as possible, although that’s far from a given. If you install third-party firmware on a Canon point-and-shoot, you get all kinds of functionality that the hardware can support but which Canon has chosen not to implement. Maybe Canon would rather you spend more money for more features, even if the cheaper hardware is perfectly capable. Maybe they just want to make common feature easy to use and not overly clutter the UI. (Not that any camera vendors are doing particularly well on ease of use, but that’s a topic for another day.)

Freedom to Tinker readers will recognize some common themes here. Do I have the right to hack my own gear? How will new technology impact old business models? In the end, when industries collide, who wins? My fear is that the creative freelance photographer, like Laforet, is likely to get pushed out by the big corporate sponsor. Why allow individual freelancers to shoot a sports event when you can just spread professional video cameras all over the place and let newspapers buy stills from those video feeds? Laforet discussed these issues at length; his view is that “traditional” professional photography, as a career, is on its way out and the future is going to be very, very different. There will still be demand for the kind of creativity and skills that a good photographer can bring to the game, but the new rules of the game have yet to be written.