Why are we spending $7 billion on TSA?

Story highlights

Bruce Schneier is a security technologist and chief technology officer of Resilient Systems Inc. His latest book is "Data and Goliath: The Hidden Battles to Collect Your Data and Control Your World." He blogs at schneier.com and tweets @schneierblog. The opinions expressed in this commentary are solely those of the author.

(CNN)News that the Transportation Security Administration missed a whopping 95% of guns and bombs in recent airport security "red team" tests was justifiably shocking. It's clear that we're not getting value for the $7 billion we're paying the TSA annually.

But there's another conclusion, inescapable and disturbing to many, but good news all around: We don't need $7 billion worth of airport security. These results demonstrate that there isn't much risk of airplane terrorism, and we should ratchet security down to pre-9/11 levels.
    We don't need perfect airport security. We just need security that's good enough to dissuade someone from building a plot around evading it. If you're caught with a gun or a bomb, the TSA will detain you and call the FBI. Under those circumstances, even a medium chance of getting caught is enough to dissuade a sane terrorist. A 95% failure rate is too high, but a 20% one isn't.
    Bruce Schneier
    For those of us who have been watching the TSA, the 95% number wasn't that much of a surprise. The TSA has been failing these sorts of tests since its inception: failures in 2003, a 91% failure rate at Newark Liberty International in 2006, a 75% failure rate at Los Angeles International in 2007, more failures in 2008. And those are just the public test results; I'm sure there are many more similarly damning reports the TSA has kept secret out of embarrassment.
    Previous TSA excuses were that the results were isolated to a single airport, or not realistic simulations of terrorist behavior. That almost certainly wasn't true then, but the TSA can't even argue that now. The current test was conducted at many airports, and the testers didn't use superstealthy ninja-like weapon-hiding skills.
    This is consistent with what we know anecdotally: The TSA misses a lot of weapons. Pretty much everyone I know has inadvertently carried a knife through airport security, and some people have told me about guns they mistakenly carried on airplanes.