To fix this, airport security has to make a choice. If something is dangerous, treat it as dangerous and treat anyone who tries to bring it on as potentially dangerous. If it's not dangerous, then stop trying to keep it off airplanes. Trying to have it both ways just distracts the screeners from actually making us safer."

Doesn't it just make sense?!

If you have ever wondered how security guards can possibly keep an unfailingly vigilant watch on every single one of dozens of television monitors, each depicting a different scene, the answer seems to be (as you suspected): they can't.

Instead, they can now rely on computers to constantly analyze the patterns, sizes, speeds, angles and motion picked up by the camera and determine -- based on how they have been programmed -- whether this constitutes a possible threat. In which case, the computer alerts the security guard whose own eyes may have been momentarily diverted. Or shut.

An alarm can be raised, for instance, if the computer discerns a vehicle that has been standing still for too long (say, a van in the drop-off lane of an airport terminal) or a person who is loitering while everyone else is in motion. By the same token, it will spot the individual who is moving rapidly while everyone else is shuffling along. It can spot a package that has been left behind and identify which figure in the crowd abandoned it. Or pinpoint the individual who is moving the wrong way down a one-way corridor.

Because one person's "abnormal situation" is another person's "hot dog vendor attracting a small crowd," the computers can be programmed to discern between times of the day and days of the week.

Certainly interesting.

There are two classes of contraband at airport security checkpoints: the class that will get you in trouble if you try to bring it on an airplane, and the class that will cheerily be taken away from you if you try to bring it on an airplane. This difference is important: Making security screeners confiscate anything from that second class is a waste of time. All it does is harm innocents; it doesn't stop terrorists at all.

Let me explain. If you're caught at airport security with a bomb or a gun, the screeners aren't just going to take it away from you. They're going to call the police, and you're going to be stuck for a few hours answering a lot of awkward questions. You may be arrested, and you'll almost certainly miss your flight. At best, you're going to have a very unpleasant day.

This is why articles about how screeners don't catch every -- or even a majority -- of guns and bombs that go through the checkpoints don't bother me. The screeners don't have to be perfect; they just have to be good enough. No terrorist is going to base his plot on getting a gun through airport security if there's decent chance of getting caught, because the consequences of getting caught are too great.

Contrast that with a terrorist plot that requires a 12-ounce bottle of liquid. There's no evidence that the London liquid bombers actually had a workable plot, but assume for the moment they did. If some copycat terrorists try to bring their liquid bomb through airport security and the screeners catch them -- like they caught me with my bottle of pasta sauce -- the terrorists can simply try again. They can try again and again. They can keep trying until they succeed. Because there are no consequences to trying and failing, the screeners have to be 100 percent effective. Even if they slip up one in a hundred times, the plot can succeed.

The same is true for knitting needles, pocketknives, scissors, corkscrews, cigarette lighters and whatever else the airport screeners are confiscating this week. If there's no consequence to getting caught with it, then confiscating it only hurts innocent people. At best, it mildly annoys the terrorists.

To fix this, airport security has to make a choice. If something is dangerous, treat it as dangerous and treat anyone who tries to bring it on as potentially dangerous. If it's not dangerous, then stop trying to keep it off airplanes. Trying to have it both ways just distracts the screeners from actually making us safer.

On the other hand, it's probably a smart idea to screen screeners when they walk through airport security when they aren't working at that checkpoint at that time. The reason is the same reason you should screen everyone, including pilots who can crash their plane: you're not screening screeners (or pilots), you're screening people wearing screener (or pilot) uniforms and carrying screener (or pilot) IDs. You can either train your screeners to recognize authentic uniforms and IDs, or you can just screen everybody. The latter is just easier.

There are two classes of contraband at airport security checkpoints: the class that will get you in trouble if you try to bring it on an airplane, and the class that will cheerily be taken away from you if you try to bring it on an airplane. This difference is important: Making security screeners confiscate anything from that second class is a waste of time. All it does is harm innocents; it doesn't stop terrorists at all.

Let me explain. If you're caught at airport security with a bomb or a gun, the screeners aren't just going to take it away from you. They're going to call the police, and you're going to be stuck for a few hours answering a lot of awkward questions. You may be arrested, and you'll almost certainly miss your flight. At best, you're going to have a very unpleasant day.

This is why articles about how screeners don't catch every -- or even a majority -- of guns and bombs that go through the checkpoints don't bother me. The screeners don't have to be perfect; they just have to be good enough. No terrorist is going to base his plot on getting a gun through airport security if there's decent chance of getting caught, because the consequences of getting caught are too great.

Contrast that with a terrorist plot that requires a 12-ounce bottle of liquid. There's no evidence that the London liquid bombers actually had a workable plot, but assume for the moment they did. If some copycat terrorists try to bring their liquid bomb through airport security and the screeners catch them -- like they caught me with my bottle of pasta sauce -- the terrorists can simply try again. They can try again and again. They can keep trying until they succeed. Because there are no consequences to trying and failing, the screeners have to be 100 percent effective. Even if they slip up one in a hundred times, the plot can succeed.

The same is true for knitting needles, pocketknives, scissors, corkscrews, cigarette lighters and whatever else the airport screeners are confiscating this week. If there's no consequence to getting caught with it, then confiscating it only hurts innocent people. At best, it mildly annoys the terrorists.

To fix this, airport security has to make a choice. If something is dangerous, treat it as dangerous and treat anyone who tries to bring it on as potentially dangerous. If it's not dangerous, then stop trying to keep it off airplanes. Trying to have it both ways just distracts the screeners from actually making us safer.

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Bruce Schneier is chief security technology officer of BT. His new book is Schneier on Security.

What’s really set me off this morning is the back and forth on the flight time. I know that there are many things that can cause a flight delay, but to move the departure time, in both directions, four times within one hour, how is that possible? I can only imagine the reaction of ScienceLogic customers if we announced the release date for the next version of the product and then proceeded to change it four times that week. There really isn’t another business in the world, other than the airlines, that could get away with this.

Assuming I eventually get to Interop NY, I will be on the look out for vendors that are working on ways to send me to my next meeting over Gigabit Ethernet!