make your own terrorists

A scientific paper on a major vulnerability to bioterrorism was withdrawn recently.
The media, very helpfully, then reported in detail what the paper was about, just in case any wannabe terrorists hadn't caught the draft paper when it came out.

This morning CNN briefly headlined an "experts predict WMD attack" pseudo-story, sometime in the next decade anyway.

So, why hasn't al Qaeda launched another attack on the US?

One possibility is that they can't. That seems unlikely, it doesn't take much, the US is still relatively porous and it wouldn't take much resources to launch high profile nuisance terrorist attacks.

One possibility is that they tried but the process was (inadvertently) interrupted. There are strong hints that a couple of attacks on the UK were interrupted; there was a news story sometime ago where an FBI agent said they thought a planned attack on US ports had been interrupted when conspirators were swept up and expelled. Insufficient evidence to actually charge anyone specific, more a overall sense of an anomaly directed at ports.

The other possibility is that aQ is patient, and is biding its time for an effective or spectacularattack. ie that they have assets in place and either still preparing, or are keeping quiet while waiting for a code word trigger.
The two latter possibilities are of course not mutually exclusive.

So, what would they do, and what could they do?

Well, aQ have stated their goal - protracted struggle with the US until the US is bankrupt and withdraws. Might as well take them at their word.
Embroiling US troops in Iraq helps the aQ there - it is a low cost operation for them, which is costing the US heavily.
More broadly, how would they damage the US economy in a long lasting manner? It is a very large, very robust economy. Even WMDs or co-ordinated infra-structure attacks would be little more than nuisances in the long run, for the US as a nation (as distinct from individual tragedies).

Well, a second war would do damage. Not clear that aQ has the leverage to trigger a second general war with the US. I'm sure they'll try a couple of places, and a couple of non-obvious places. But the US administration would have to be pretty stupid to get drawn into another provocation...

The only other leverage is to get the US to destroy itself - either by destroying US public confidence, triggering an economic depression through fear and prolonged consumer conservatism; or, the other way is to lever the US legal system to trigger long term economic damage - forcing repression, choking innovation, reducing mobility, increasing useless regulation and artificial high cost, and generally useless, security measures.
Such might be triggered by multiple high emotional impact terror attacks: schools, hospitals, sporting events, other soft targets.
There are very few infrastructure targets which are so unique and so hard to rapidly replace that there'd be actual lasting damage; might be able to think of a few, but such things really are surprisingly resilient and replacable, unless the associated psychological impact precludes action to fix the situation.
And it would be highly imprudent to openly say what the few might be, even if I'm wrong, as I most certainly would be.

Finally, there is the question of what aQ has? Do they have a handful of people? Tens? Hundreds? Larger numbers who'd mobilise on the street if asked (I don't think they have thousands of people in the US actually willing to committ felonies, but civil disobedience by many, co-ordinated with terrorism by few, is a potentially effective tactic).

What resources do they have? Tens of thousands of $? Hundreds of thousands? Millions? Hundreds of millions?
What they can do is very sensitive to the asset level and whether the money can be channeled to the users.
I suspect the high end here. They have donors with real money, and there are too many ways in which a lot of money can be moved into place. Simplest way would be to buy up legitimate businesses, even as part of legal immigration requests. Use them as revenues streams and realisable assets, even as infrastructure. If I were aQ I'd buy a light truck franchise or two, and some general stores in friendly neighbourhoods. With medium workforces, slowly turned over; warehouses behind fences, steady traffic and on-site workshops and their own, familiar to all, transport.

Finally what tools? Certainly light firearms, up to AK47s and field improvised explosives and incinerants.
Do they have light infantry weapons inside the US? (Mortars, claymores, plastic explosives, machine guns? People trained to use them in place inside the US?)
Heavy weapons (armoured vehicles and artillery - very hard to arrange unless they completely infiltrated a national guard unit or some such, hard to hide)? Would be surprised if they had air - though buying a small cargo/charter carrier wouldn't be inconceivable. Easier to have some sea transport; again they'd need to own a smallish company with own assets engaged in long term legitimate trafficking. Tricky, but not impossible.

Special weapons? Most WMDs are overrated in impact - even nuclear weapons do just local damage if used singly.
Radiological weapons are more a nuisance, and chemical weapons are hard to deploy in significant quantities.
The possibilities that threaten are biological weapons, if done effectively, which is hard by all accounts. Economic biological weapons - eg hoof & mouth disease, are a bigger economic threat than many higher profile bioweapons targeted at people.

Main impact of special weapons is the psychological impact. The sense of vulnerability for the public. The Ickyness factor, and propensity of authorities to overreact or misreact. Which is the leverage they'd have on the US economy as a whole.

Finally, one wonders if aQ learned one of the primary IRA lessons - for terror, you maximise the threat by having a significant number of false alarms per real attack. Not too many, just enough to maximise uncertainty and fear.
Of course the terrorists will still most likely lose. In so far as a victory for either side can be defined in such circumstances.
Eventually.