Can you (or a populace) be influenced by something you are unaware of? If so, you can be a victim of an act terrorism without knowing of the act.
If a terrorist shoots my sister, and nobody knows it was a terrorist plot, the destabilization and other negative effects are still there. I will be afraid, perhaps not of ISIS, but I will generally be terrified that someone might shoot me too.
Terrorism is not so simple. Thinking that all terrorism must be some extreme, singular act seems short-sighted. What is the terrorist's goal?
Terrorism can be subtle and long-term.
Edit: What terrifies you? Did terrorists exclusively create this (threat of terror)? My point is, does a terrorist exclusively create terror... or do these terrorists have a broader goal beyond simple terrorism?
