I'm watching CNN today and they have moved on from shouting about the dangers of refugees (finally) to the VWP: VISA Waiver Program. VWP IS GOING TO DESTROY AMERICA!
The VWP is pretty secure, and even more so with changes made in the wake of 9/11. It is used by foreign travelers to come here for up to 90-days for business or pleasure (the State Department does not mention for terror. Odd).
To get it you needs to jump a bunch of hurdles. On CNN an "expert" said he thinks may six or so could have gained entry through the program. I doubt it. The chance of a terrorist getting through on VWP is very very unlikely.
VWP is given to citizens of nations that have similar agreements with us. That is thirty-eight countries and only one is in the Middle East (Brunai). No Syria or other sponsors of terrorism. If you ever traveled to one of these nations you will never get the VWP. Period. One of the terrorist in Paris was from Belgium. Even though he was a naturalized citizen of Belgium, he would never have been granted a VWP.
In order to be eligible you need an e-passport. That is a very secure password with a chip that contains your bio-data and records. The terrorist that entered Greece came in with a fake passport but it was not an e-passport. He would not have been able to fake it.
Then you are ran on the Interpol database, the terror watch list, the no-fly list, and others. A flag comes up, no VWP for you. Also, you will rejected for just about any criminal act you were convicted of within five years.
You also need to have significant holdings in the country you are coming from (a house, etc.).
If you do not meet anyone of these for any minor reason, you need to apply for a regular VISA, which takes much more time. This program is not unlike the pre-checking in for a domestic flight so you don't have to go through all the rigmarole every time you fly.
So stop worrying about one in a million scenarios. Let's start thinking what really needs to be done.
I am sure the news networks will move on in a few days to the next big scare to keep your eyes glued to the screen.