I see someone's completely circumvented all the "security" in US airports.
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Apparently the FBI has been "testing" "security" in US airports by posing as pasengers and doing naughty things. Meanwhile, some "prankster" just walks on, and leaves a bag of knives and clay (with a letter) in the toilet of two planes.
It suprises me that the FBI and airports hadn't figured this out already. In my meagre experience of US airports, it seems to me that the whole security premise is "rock ridge". It's typically American - lots of show, and not really a lot of substance.
For example, a friend of mine was searched three times getting onto one flight. This is clearly inefficient, and implies that two of the three checks were flawed (otherwise, why check more than once?). Also, the searches are not thorough - they're designed for show rather than effect. The security in US airports largely rests on the belief that they are secure and that they cannot be breached, as opposed to the reality of security.
For the average person travelling around, we're not really that interested in how the security works. We trust that it's effective, and we don't generally question it or check it (because either of those acts can see retribution brought upon the perpetrator). As a result, almost any minor inconveniences along the way to an aeroplane would make the average person think that security was tight.
Whilst I'm no terrorist, I do work with IT security. From the hacker point of view, you study a situation, learning as much as you can about the scenario in front of you. Then, bit by bit, you break it down into parts, within which you look for weaknesses. The linkage between parts is also important, and some seemingly unimportant detail may prove useful elsewhere. (for example, getting the system time legitimately from one service and use it to attack another).
It seems to me, that any concerted terrorist could find weaknesses in airport security. There are some things allowed through security without checks, for example. Whilst it's unlikely you could transport large quanitities of any contraband through security, you could, bit by bit achieve quite a lot. I'm thinking sort of on the lines of the Great Escape - a little, but often, and eventually you get there.
Whilst I might be quick to criticise US airport security, I suspect that other countries are the same. I imagine the difference is that those countries do not arrogantly assume their security is flawless.
In short, whilst there is no specific threat in place, you're only a victim by random chance. If there is a specific threat, then be very careful about what you do.