Unfortunately this will lead to strict checks and possible deportation of some who might have no bad intention at all. World works on some level of basic trust. If people break and not follow then this world will become a mess. People should understand the war also needs to follow rules, else we are going back to medival ages.
Nothing will happen.
Everyone will pretend the attacks are ghastly, give some politically correct speeches and go to sleep until the next attack. Rinse & repeat.
This is not the first and won't be the last.

, focus more on the matter rather than bieng an editor of words, or maybe thats ur favourite escape route...there is a fat toad altaf sitting in Uk protected by the english govt, a uk citizen who has orchestrated the murder of thousands in karachi, how is he different than osama bin ladin??, why does the uk turn a blind eye towards that??, they are harbouring a terrorist, but its ok when pakistanis are getting killed, right??....ur hypocracy stinks to high heavens....