How will aggro be on mobs?

[Felis]

It appeared to me from the Alpha vids that its pretty similar to how it was in 1.0, with the exception that ARR seems to put a large red icon over ANY mob that is considered aggressive. From that, it looks like you'll be able to tell if a mob is aggressive from a mile away, although how it aggros is still up in the air.

This was already in 1.x. you could turn the icon off