Thursday, 7 January 2010

If you've something irrelevant to hide, you've everything to fear

[trigger warning]

Following the recent bombing attempt late last year, the UK government has said that it wants to make "full body scanners" required at all airports. They've been described as "virtual strip searches", which is a pretty accurate description from the photographs released of their operation.

They of course differ from a real strip search in a number of respects:

  • The process only takes a few seconds, and so is feasible to implement for everyone.
  • The process only takes a few seconds, and so it's going to be a lot easier for busy staff to miss something.
  • Because it consists of stepping into a device rather than going through the process of removing clothes, a significant number of people will just do it.

The similarities are more important than the differences, however.

Here's a quote from the Guardian:

Staff at Manchester airport pointed out that the images were deleted "within seconds" of being captured and checked and could not be stored.

It's almost certainly completely true that the scanner system itself displays the images and then deletes them. Careful design can ensure that the image data is never stored anywhere by the scanner system.

It is, however, displayed on a screen, for sufficient time for the operator to glance over it for explosives, suspicious objects, and numerous false positives. That's also long enough to snap a picture with a digital camera, especially with the suggestion of placing the operator in a separate room free from distractions to counteract the second point above.

The major problem with these devices - as with any search wildly disproportionate to the reasonable level of suspicion one might have - is that "nothing to hide" is quite a bit stronger than "nothing terrorism-related to hide". At least 99.99999% of air passengers are not terrorists (or at worst, are off-duty terrorists). The proportion of passengers who could be outed as intersex or trans or have some medical condition revealed is at least 1%. The Guardian article mentions that 92% of passengers are happy to be scanned this way. The governmentseems to be ignoring the obvious problem with this statistic:

  • The 92% of passengers who are happy to be scanned have nothing to hide of any sort.
  • The other 8% presumably have something to hide, which in many cases will be as straightforward as "what they look like naked". Of those 8%, fewer than 1 in 100,000 will be hiding anything terrorism related.
  • Therefore, for every terrorist caught, there will be around 100,000 unwanted invasions of privacy. We can add to that the various people in the 92% who don't want to be seen naked by security staff but are coerced into it out of fear that failing to do so will raise suspicion and be considerd cause for a physical strip search.
  • If we felt a 100,000:1 ratio of invasions of privacy to successes was reasonable as a society, then we'd just institute randomised crime searches: the police pick a random address, thoroughly search it - without the need for a warrant - for evidence of crimes, make any consequent arrests, and move on to the next random address.

All terrorism attempts in this country in recent years have been stopped significantly before the stage of "getting explosives onto a plane", which as has been said is about the only terror-related thing you can do with planes nowadays that stands a chance of working.

There have been terrorism attempts in this country in recent years that have succeeded in causing deaths or injuries. The major thing they've had in common - from the 7 July bombers to the various paramilitary groups in Northern Ireland - is a distinct lack of planes. Even the Glasgow attack (which wasn't very successful) didn't quite involve planes. This says to me that - in the UK, anyway - airport security, combined with anti-terrorism investigations, is already more than sufficiently strong to prevent terrorist attacks on aircraft.

Given that, introducing further security measures that will probably, over the next ten to twenty years, prevent absolutely no terrorism whatsoever, but put several people's lives at risk for other reasons, seems the worst sort of security theatre. If the government feels that routine strip searches of passengers are genuinely necessary to the security of aircraft then they should just institute routine physical strip searches of all passengers at airports. Perhaps that would make it clearer just how disproportionate this is.