Maybe they've smartened up about the NSA and started a program of illusory attacks...which in themselves have a terrorizing aspect, weaken the image of America, and makes it look like al-Qaeda is astride a Strong Horse.
Or maybe they are probing just how effective the NSA actually is.
Perhaps they are utilizing both your options. Pretty soon, al Qaeda could get the entire USA shut down with some frivolous threats. They could do so without even using just one suicide bomber. Yet without a terrorist incident, al Qaeda can’t advertise, “we offer jihadists more bang for your bucks.”
Or maybe now that they’ve “beefed up” security, they’ll find a reason to leave the agents in place.
(every “alert” is another opportunity to pad the union voter base)