The uncovering of an alleged plot involving the Khayat brothers to bring down an airliner or launch some sort of toxic gas attack in Sydney should prompt a serious rethink about how effective we are at protecting ourselves from terrorism and why we're spending so much money doing so.

If police allegations and leaks from within security agencies are true -- and we have previously seen lurid charges of terror plots levelled against individuals either proven to be wrong or wildly overstated before -- the poison gas attack appears to have been wildly ambitious, but the plan to bomb an Etihad flight, using another of the brothers as an unwitting mule for a bomb, was only a couple of steps from succeeding.