This article is worth reading because the front lines are now churches and cafes and Christmas markets and anywhere people congregate.
I have two further thoughts on this:
1) ISIS understands that Christmas is a deeply Christian observance. They attack us because we are the "people of the cross" who worship the Savior born in Bethlehem. That means the war on terror is in not only a war of sudden attacks. It's also a form of spiritual warfare. Sometimes I think the bad guys understand this (in their evil way) better than we do.
2) Every church needs to have a security team and a security plan in place. Not just for this weekend but for every Sunday and every public service. When I went to seminary 40 years ago, I never heard a word about church security. But times have changed. No church is too small to be attacked. We need not live in fear, but we ought to take prudent steps to protect the people who come to our services.