No, you don't know that. Scum of the earth comes from all countries, the US and Israel included. FWIW, though, the most realistic scenario I can think of is that they may have had knowledge that something was going to happen, though maybe they didn't know the wheres and whens.
But, on the other hand, you can't discount the possibility that they did know exactly where and when.
Why can't some people even concede the possibility of Israeli terrorists? I don't have any idea how probable it is, but it's certainly possible. There are people in every single country on this earth who would kill their own mothers if it would further their own agendas.
The US must leak like a sieve on intelligence matters in general, so is it unlikely that even our friends would be spying on us? Heck, Monica Lewinsky and even Chandra Levy might've been Israeli agents. Clinton and Condit sure seemed ripe for the picking.
We should just assume it's being done, though continue our commitment to one of the only countries in the world that continues to seize the initiative to act, as opposed to perpetual victims who'd rather sit around on their hands, or blackmail the world by terror, demanding that statehood and/or respect merely be handed them.