Story highlights This week, the TSA announced a large electronics ban on travel from eight Muslim countries

Bruce Schneier: When faith in government is at an all-time low, many Americans are skeptical this is a justified security measure

Bruce Schneier is a lecturer at the Harvard Kennedy School and a fellow at the Berkman-Klein Center for Internet and Society. He blogs at www.schneier.com. The views expressed in this commentary are his own.

(CNN) On Monday, the TSA announced a peculiar new security measure to take effect within 96 hours. Passengers flying into the US on foreign airlines from eight Muslim countries would be prohibited from carrying aboard any electronics larger than a smartphone. They would have to be checked and put into the cargo hold. And now the UK is following suit.

It's difficult to make sense of this as a security measure, particularly at a time when many people question the veracity of government orders, but other explanations are either unsatisfying or damning.

Bruce Schneier

So let's look at the security aspects of this first. Laptop computers aren't inherently dangerous, but they're convenient carrying boxes. This is why, in the past, TSA officials have demanded passengers turn their laptops on: to confirm that they're actually laptops and not laptop cases emptied of their electronics and then filled with explosives.

Forcing a would-be bomber to put larger laptops in the plane's hold is a reasonable defense against this threat, because it increases the complexity of the plot. Both the shoe-bomber Richard Reid and the underwear bomber Umar Farouk Abdulmutallab carried crude bombs aboard their planes with the plan to set them off manually once aloft. Setting off a bomb in checked baggage is more work, which is why we don't see more midair explosions like Pan Am Flight 103 over Lockerbie, Scotland, in 1988.

Security measures that restrict what passengers can carry onto planes are not unprecedented either. Airport security regularly responds to both actual attacks and intelligence regarding future attacks. After the liquid bombers were captured in 2006, the British banned all carry-on luggage except passports and wallets. I remember talking with a friend who traveled home from London with his daughters in those early weeks of the ban. They reported that airport security officials confiscated every tube of lip balm they tried to hide.

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