• Low-tech is very effective. Movie-plot threats -- terrorists with crop dusters, terrorists with biological agents, terrorists targeting our water supplies -- might be what people worry about, but a bunch of trained (we don't really know yet what sort of training they had, but it's clear that they had some) men with guns and grenades is all they needed.

• At the same time, the attacks were surprisingly ineffective. I can't find exact numbers, but it seems there were about 18 terrorists. The latest toll is 195 dead, 235 wounded. That's 11 dead, 13 wounded, per terrorist. As horrible as the reality is, that's much less than you might have thought if you imagined the movie in your head. Reality is different from the movies.

• Even so, terrorism is rare. If a bunch of men with guns and grenades is all they really need, then why isn't this sort of terrorism more common? Why not in the U.S., where it's easy to get hold of weapons? It's because terrorism is very, very rare.

• Specific countermeasures don't help against these attacks. None of the high-priced countermeasures that defend against specific tactics and specific targets made, or would have made, any difference: photo ID checks, confiscating liquids at airports, fingerprinting foreigners at the border, bag screening on public transportation, anything. Evenmetal detectors and threat warnings didn't do any good:

  "If I look at what we had, which all of us complained about, it could not have stopped what took place," he told CNN. "It's ironic that we did have such a warning, and we did have some measures."

  He said people were told to park away from the entrance and had to go through a metal detector. But he said the attackers came through a back entrance.

  "They knew what they were doing, and they did not go through the front. All of our arrangements are in the front," he said.

If there's any lesson in these attacks, it's not to focus too much on the specifics of the attacks. Of course, that's not the way we're programmed to think. We respond to stories and not analysis. I don't mean to be sympathetic; this tendency is human and these deaths are really tragic. But eighteen armed people intent on killing lots of innocents will be able to do just that, and last-line-of-defense countermeasures won't be able to stop them. Intelligence, investigation, and emergency response. We have to find and stop the terrorists before they attack, and deal with the aftermath of the attacks we don't stop. There really is no other way, and I hope that we don't let the tragedy lead us into unwise decisions about how to deal with terrorism.

An internal memo obtained by The Associated Press says the FBI has received a "plausible but unsubstantiated" report that al-Qaida terrorists in late September may have discussed attacking the subway system.

[...]

The internal bulletin says al-Qaida terrorists "in late September may have discussed targeting transit systems in and around New York City. These discussions reportedly involved the use of suicide bombers or explosives placed on subway/passenger rail systems," according to the document.

"We have no specific details to confirm that this plot has developed beyond aspirational planning, but we are issuing this warning out of concern that such an attack could possibly be conducted during the forthcoming holiday season," according to the warning dated Tuesday.

[...]

Rep. Peter King, the top Republican on the House Homeland Security Committee, said authorities "have very real specifics as to who it is and where the conversation took place and who conducted it."

"It certainly involves suicide bombing attacks on the mass transit system in and around New York and it's plausible, but there's no evidence yet that it's in the process of being carried out," King said.

Knocke, the DHS spokesman, said the warning was issued "out of an abundance of caution going into this holiday season."

Got that: "plausible but unsubstantiated," "may have discussed attacking the subway system," "specific details to confirm that this plot has developed beyond aspirational planning," "attack could possibly be conducted," "it's plausible, but there's no evidence yet that it's in the process of being carried out."

I have no specific details, but I want to warn everybody today that fiery rain might fall from the sky. Terrorists may have discussed this sort of tactic, and while there is no evidence yet that it's in the process of being carried out, I want to be extra-cautious this holiday season. Ho ho ho.

This is just ridiculous. Of course the bad guys will use all the communications tools available to the rest of us. They have to communicate, after all. They'll also use cars, water faucets, and all-you-can-eat buffet lunches. So what?

This commentary is dead on:

Steven Aftergood, a veteran intelligence analyst at the Federation of the American Scientists, doesn't dismiss the Army presentation out of hand. But nor does he think it's tackling a terribly seriously threat. "Red-teaming exercises to anticipate adversary operations are fundamental. But they need to be informed by a sense of what's realistic and important and what's not," he tells Danger Room. "If we have time to worry about 'Twitter threats' then we're in good shape. I mean, it's important to keep some sense of proportion."

I'm skeptical, of course. But read his post; it's interesting.

Item 2: Hawley responded to my response to his blog post about an article about me in The Atlantic.

Item 3: The Atlantic is holding a contest, based on Hawley's comment that the TSA is basically there to catch stupid terrorists:

And so, a contest: How would the Hawley Principle of Federally-Endorsed Mediocrity apply to other government endeavors?

Not the same as my movie-plot threat contest, but fun all the same.

Item 4: What would the TSA make of this?

It is thought Islamist extremists are concealing messages in digital images and audio, video or other files.

Police are now investigating the link between terrorists and paedophilia in an attempt to unravel the system.

It could lead to the training of child welfare experts to identify signs of terrorist involvement as they monitor pornographic websites.

Of course, terrorists and strangers preying on our children are two of the things that cause the most fear in people. Put them together, and there's no limit to what sorts of laws you can get passed.

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.

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.

---

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