Look who's on the board of directors:http://www.nti.org/b_aboutnti/b1_board.html
Look at this insane indoctrinating psyop bullsh*t:http://www.nti.org/e_research/cnwm/overview/path.asp
Maximizing the chance of preventing a terrorist attack with a nuclear weapon requires systematically thinking through each step terrorists would have to take on the pathway to a nuclear attack, and putting in place a multi-layered defense focused on blocking them every step of the way.
The most critical choke-point on that pathway, where actions that can be taken now can do the most to reduce the risk, is in preventing nuclear weapons and materials from being stolen in the first place. As former Senator Sam Nunn has said:
The most effective, least expensive way to prevent nuclear terrorism is to secure nuclear weapons and materials at the source. Acquiring weapons and materials is the hardest step for the terrorists to take, and the easiest step for us to stop. By contrast, every subsequent step in the process is easier for the terrorists to take, and harder for us to stop
That is why homeland security and the defense against catastrophic terrorism must begin with securing weapons and fissile materials in every country and every facility that has them. Yes, this is an awesome challenge, but it is finite and doable.
This figure outlines the key steps on the terrorist pathway to attack with a nuclear weapon, and highlights the elements of the war on terrorism, homeland security, and cooperative threat reduction programs that are intended to block each of these steps on the path. Some scenarios would sidestep one or more of the steps on this pathway; as the figure shows, for example, if a state were willing to provide a nuclear weapon or weapons material to the terrorist group, this would get the terrorists past several of the key obstacles they would otherwise face. (For a discussion of why that scenario is unlikely, see "Will States Give Terrorists the Bomb?") Similarly, if terrorists stole nuclear material within the target country and assembled it there, this would sidestep several of the steps in the pathway. Nevertheless, the set of steps outlined below is representative of the key obstacles a terrorist group would have to overcome to acquire and set off a nuclear weapon, and the key opportunities for stopping them from reaching that objective.
Step 1: Form a Highly Capable Group With Extreme Objectives
Most terrorist groups simply would not have the capability to take all the steps required to get and use a nuclear bomb. This is not a type of attack that Timothy McVeigh and his co-conspirators could plausibly have accomplished. An operation on this scale would require a sophisticated group capable of an operation requiring substantial planning, sustained preparation over a long period of time, absolute secrecy among the participants, and significant technical know-how (recruited or bought).
The most authoritative unclassified discussion of the possibility that terrorists might make a nuclear bomb concludes that the team to design and make the bomb would have to include at least three to four individuals, possibly more, with expertise ranging from physics to explosives to the metallurgical properties of the plutonium or uranium to be used not the typical expertise of most members of a terrorist group. A substantial amount of money would be needed, to purchase a nuclear weapon or materials to make one from people who had stolen it (or to arrange for the theft to take place), to provide the equipment needed to fabricate a bomb (if the group were making one from nuclear material), and to pay the various individuals involved while the operation was underway. Some form of safe haven, a base where the group could plan, work on its design, make bomb parts and confirm that they worked, and the like would be extremely useful (see discussion below).
Thus, the first step toward a terrorist attack with a nuclear weapon is the formation of a sophisticated, capable, and well-financed terrorist group and one with the kinds of extreme objectives that would make it a candidate for deciding to pursue a nuclear attack (see discussion below).
Unfortunately, al Qaeda has already taken this step. They have demonstrated, with the September 11 attacks and others, a substantial degree of sophistication, a considerable capacity to collect intelligence on opponents' weak points, an ability to plan and train for attacks for well over a year beforehand, an ability to maintain secrecy and strike without warning, and an impressive knowledge of explosives (as was needed, for example, to blow a huge hole in the side of the heavily armored U.S.S. Cole). Today, however, there is no evidence that al Qaeda has the technical knowledge of nuclear matters that would be needed to make a nuclear bomb though we cannot know for sure that they do not.
A wide range of U.S. actions can address this fundamental first step in the chain. As our figure shows, these steps are mainly in the domain of the war on terrorism. First, to prevent other groups from following al Qaeda on this path, there is much to be done to address the root causes of terrorism the regional, political, religious, and ethnic conflicts that breed the necessary hatred, the poverty, and the humiliation that foster desperation and violence. A just resolution of the Israeli-Palestinian conflict, coupled with equitable economic and political development in the Arab world, would probably do as much to reduce the risk of catastrophic terrorism in the United States as any other events that could occur. As Phillip Heymann has noted, actions to reduce the degree of hatred for the United States probably cannot succeed in preventing terrorist groups from recruiting enough people to pose a serious danger to U.S. interests but may be essential to allow key states to crack down on terrorists within their borders without provoking regime-threatening domestic opposition.  Similarly, there is much to be done to continue to build global support for the norm against terrorism, to make terrorist action a less and less acceptable means for achieving political or other ends.
Second, intelligence and other counter-terrorism efforts can and should focus on identifying, monitoring, disrupting, and destroying the small subset of terrorist groups with the sophistication, finances, and extreme objectives that could lead to truly catastrophic attacks including nuclear attacks. The U.S. response since the September 11 attacks has surely done a great deal to make it more difficult for al Qaeda to carry out an operation with all the requirements involved in getting and using a nuclear bomb and therefore has significantly reduced the risk. That risk has by no means been eliminated however. In particular, U.S. intelligence has concluded that al Qaeda has been reconstituting in the mountains of Pakistan's largely ungoverned tribal areas; that al Qaeda retains the ability to organize large and complex attacks; and that the group retains a "persistent desire" for nuclear, chemical, biological, and radiological weapons, and "continues to try" to acquire them.
Third, by word and deed, the United States and its partners should continue to attempt to deter other states from sponsoring and offering havens for terrorist groups, particularly those with the substantial capabilities and extreme objectives that could contribute to truly catastrophic attacks. President Bush's immediate statement that those states that were not with us in the war on terrorism were against us, combined with the quick destruction of the Taliban regime in Afghanistan, surely sent a powerful message to other states around the world, increasing their incentive to cooperate with the United States in fighting terrorism, and possibly deterring some from sponsoring or providing havens for groups that might launch large attacks against U.S. interests. Unfortunately, the war in Iraq has increased anti-American hatred around the world, and made it more politically costly for many governments in the Islamic world to be seen as cooperating with the United States.
Step 2: Decide to Escalate to the Nuclear Level of Violence
Most terrorist groups would have no interest in escalating to the ultimate violence of detonating a nuclear weapon in a major city. They are focused on specific political objectives such as independence for Northern Ireland or the Basque area of Spain whose achievement would only be undermined by escalating from car bombs in marketplaces to a nuclear attack. Their specialty, in short, is retail violence, not wholesale violence. As terrorism expert Brian Jenkins famously remarked decades ago, "terrorists want a lot of people watching, not a lot of people dead."
Only groups motivated by a brand of religious extremism they see as calling for mass destruction of non-believers, or groups with objectives on a global scale, are likely to be strong candidates for escalating to the nuclear level of violence. Here, too, unfortunately, al Qaeda is different from most terrorist groups. The leaders of al Qaeda have made their desire to inflict mass destruction on Americans and their allies very clear, by both words and deeds. This desire is driven by extreme global, religiously based objectives, specified in some detail in their public statements specifically, ejecting the United States and other infidels from the Middle East, replacing the secular regimes of the Arab world with fundamentalist Islamic regimes, and destroying Israel. Similarly, Aum Shinrikyo, the Japanese terror cult that launched a nerve gas attack in the Tokyo subways and sought nuclear weapons, was focused on a religious nihilist vision of bringing on a cleansing Armageddon by launching catastrophic attacks.
Once a highly capable group of this scale has formed, and adopted the kinds of extreme objectives that might justify nuclear violence, there may be little the United States can do to influence the internal decision-making of the group on whether or not to pursue a nuclear weapon option though even in the case of large and extreme terrorist groups, deterrence can work some of the time, and should remain one element of the counter-terrorism toolkit. But the United States and its partners can and should focus an intense intelligence collection and analysis effort on identifying and learning as much as possible about groups with the kinds of objectives that make them plausible candidates for escalating to weapons of mass destruction followed by an intense effort to disrupt and destroy them, wherever they may be. Efforts to infiltrate such groups or to recruit agents from them, if successful, would be particularly valuable in providing information on their goals and activities related to weapons of mass destruction. Here, too, as shown in our figure, the key efforts to disrupt the terrorist pathway to the bomb are elements of the war on terrorism.
Step 3: Thieves Steal Nuclear Weapon or Weapons Material
Unless a state consciously transfers a nuclear weapon or the material to make one to a terrorist group (see "Will States Give Terrorists the Bomb?"), the next essential step is for a nuclear weapon or nuclear material somewhere to be stolen. One option would be for the terrorists to carry out the theft themselves either by attacking a facility that had what they wanted, or by attempting to infiltrate the staff of such a facility so as to carry out an insider theft. (Terrorists might also bribe or coerce existing staff at such a facility into carrying out an insider theft, or providing insider help to an outsider attack; kidnapping a family member of a key guard or staffer, for example, and threatening to harm them if their demands were not met, would be one obvious possibility.) Such an incident is by no means inconceivable: the commander of the force that guards Russia's nuclear weapons, for example, has said publicly that terrorist groups carried out reconnaissance at Russian nuclear warhead storage sites sites whose very locations are state secrets, but apparently were known to the terrorists twice during 2001. 
None of the known cases of nuclear theft to date, however, involve direct theft of nuclear materials by or for a terrorist group or the agents of a hostile state. Instead, they involve opportunistic thieves, who stole nuclear material with the idea of being able to sell it later. To date, this threat has been entirely a matter of insiders walking off with material to which they have authorized access.
This is the step in the pathway that can most directly and reliably be stopped. If effective security and accounting arrangements, capable enough to defeat all the threats a facility is likely to face, are put in place for every nuclear weapon and every kilogram of weapons-usable nuclear material throughout the world, the threat of nuclear weapons terrorism can be dramatically reduced. Accomplishing that task at the hundreds of buildings around the world where these weapons or materials exist is a big job, and will be a complex job, given the need to forge highly sensitive security partnerships with each of the countries where this material exists. But it is a doable job. The technology is not a mystery: humankind has been guarding particularly valuable or dangerous materials for a long time (though there are new technologies that can make security even stronger). By contrast, once the material has been stolen, the number of places where it could be jumps from hundreds to millions: unless some participant in the conspiracy provides critical intelligence on where to look or unless the relevant government gets lucky finding and recovering stolen nuclear material poses an almost insuperable challenge.
This, then, is the reason for the enormous importance of threat reduction programs: as our figure shows, these are the key efforts that can help disrupt this critical step in the terrorists' pathway. Cooperative threat reduction programs contribute in a number of ways to blocking thieves from stealing fissile material or intact nuclear weapons (each of the specific programs in the various government agencies that contribute in some way to each of these goals are discussed in this website's section on that goal).
Programs aimed at securing nuclear warheads and materials both by providing secure storage and transportation and on removing nuclear weapons or weapons-usable material from potentially vulnerable sites seek to ensure that every nuclear weapon and every kilogram of weapons-usable nuclear material worldwide is secure and accounted for, directly reducing the terrorists' chances of getting a stolen nuclear warhead or nuclear material. Security for these stockpiles must be effective in preventing either outsiders or insiders or both working together from stealing them, and must be designed to be sustained for the long haul.
Because even the best security system is only as good as the people who run it, another crucial goal is stabilizing employment for nuclear personnel, in order to ensure that nuclear scientists, workers, and guards are not desperate enough to want to steal nuclear weapons and materials or sell nuclear knowledge, and to close unsustainable and unnecessary nuclear facilities, so that stronger and more sustainable security can be achieved at the remaining facilities.
The direct purpose of most proposed measures aimed at monitoring stockpiles and reductions is to confirm that agreed nuclear reductions are being implemented. But these measures can have substantial indirect benefit in reducing the risk of theft of nuclear weapons and materials, easing the access that facilitates cooperation, highlighting weaknesses in security and accounting, and providing an incentive to fix potentially embarrassing problems before they are revealed. Overall, the goal here should be to put in place sufficient monitoring and data exchanges to build confidence that nuclear stockpiles are secure and accounted for, agreed reductions are being implemented, and assistance funds are being spent appropriately.
With the end of the Cold War, the United States and Russia have far more nuclear weapons and weapons material than they could possibly need, and so they should stop making more. Cooperative programs focused on ending production, if successful, will put a cap on the total amount of nuclear material that has to be guarded from terrorists and thieves.
Similarly, other cooperative programs are working to reduce the massive excess stockpiles of nuclear weapons and weapons-usable nuclear material, so that unneeded stockpiles do not have to be guarded forever. This is a long-term objective, however, and a building with a ton of weapons-usable nuclear material poses nearly the same theft risk as a building with 100 tons, so these programs will only reduce the risk of nuclear theft if they lead to reductions in the number of buildings where potential nuclear bomb material might be stolen, and the number of people with access to that material.
Step 4: Acquire Nuclear Weapon or Weapons Material From Thieves
The next crucial step is for the terrorists to acquire the stolen nuclear weapons or material from those who stole it. (This step could be skipped if the theft were carried out directly by, or on behalf of, the terrorist group, in which case the group would presumably take possession of the stolen items immediately.) In the known cases of theft of nuclear material, this step has proved to be a difficult one. Nuclear thieves and those who might like to buy from them have had difficulty finding each other. Both parties face the risks of being turned in by co-conspirators, ripped off by con artists or unscrupulous middle-men, or trapped in government sting operations. In the known cases, stolen nuclear material has generally been seized when one of the co-conspirators, or some one they tried to sell the material to, informed on the thieves or the smugglers or when the theft was provoked by a government sting in the first place. Al Qaeda appears to have been scammed in its attempt to buy HEU in Sudan in 1993, and there are reports that it has lost money in other nuclear scams as well. Similarly, Iraqi nuclear defector Khidir Hamza has reported that Iraq attempted to get stolen nuclear material, but was repeatedly confronted with sellers attempting to pass off junk material, and was concerned over the risk of getting caught in a sting operation.
There is a good deal that governments can do to make this step even more difficult and risky for terrorists and thieves to accomplish. Sting operations (undercover agents posing as thieves, posing as buyers, and posing as middle-men), a wide range of techniques to encourage conspirators to turn each other in, and increases in the legal penalties for anyone convicted of being involved in such operations are all worth pursuing. Most of the possible actions to intercept this step fall into the domain of intelligence and law enforcement including international cooperation and sharing of key information.
Cooperative threat reduction programs are also useful in blocking this step. Programs focused on interdicting nuclear smuggling provide the next line of defense, by maximizing the chance that a nuclear weapon or weapons-usable nuclear material, once stolen, could be found and recovered, and efforts to smuggle such items between countries could be detected and stopped. Where the focus is keeping nuclear weapons or materials from entering the United States, or finding them once there, these efforts are in the province of homeland security programs.
In addition to helping to prevent theft of the material in the first place, programs working to stabilize employment for nuclear personnel can help block this step, by reducing the pool of knowledgeable experts who may be willing to participate in such a conspiracy, forcing thieves, middle-men, and buyers to draw from a smaller and potentially less reliable pool for expertise that may be useful to smooth the transaction. 
Step 5: Smuggle Nuclear Weapon or Weapons Material to Safe Haven
Next, in most cases the stolen nuclear weapon or weapons material would have to be smuggled from the country where it was stolen to a terrorist safe haven where the stolen items would be prepared for use. This involves crossing international borders, creating at least a chance for effective border and customs controls to detect and stop the shipment.
Unfortunately, a range of factors conspires to make stopping nuclear weapons or materials at international borders an extraordinarily difficult challenge, including:
The enormous length thousands of kilometers of the main borders nuclear material might cross;
The enormous scale of legitimate border crossings, amounting to millions of people and vehicles crossing the relevant borders every year;
The huge scale of ongoing smuggling of other items, from arms to drugs to cigarettes, which governments have been unable to stop;
The possibility of observing which border crossings are effectively monitored, and bypassing them;
The weaknesses of many of the relevant customs and border control forces, from limited manpower to low pay to endemic corruption;
The small amount of small amount of material needed for a bomb an amount roughly the size of a soda can; and
The low levels of radiation the nuclear materials used for nuclear weapons emit, which makes it very difficult to detect them unless you know exactly where to look.
Despite these daunting challenges, it is important to make at least some investment in providing additional lines of defense should nuclear weapons or materials be stolen despite efforts to secure them. This is particularly important as there is no way of knowing how much nuclear material may already have been stolen without detection.  This is where the range of threat reduction programs under our interdicting nuclear smuggling heading play their biggest role, training and equipping law enforcement, customs, and border control forces in relevant countries to interdict nuclear smugglers. Expanded international law enforcement and intelligence cooperation focused on blocking nuclear smuggling including, again, intelligence operations such as stings, to help deter the smugglers by increasing the fear of being caught are urgently needed. Because of the massive scale of the challenges, it is crucial, in pursuing these efforts, to identify the highest priority tasks (such as the border points most heavily trafficked by smugglers) and focus on those, rather than wasting resources attempting to do everything. But it is also crucial to take a systems approach that explicitly considers the many adversary options for defeating the defenses, and the defense options for responding. 
Step 6: Construct Weapon or Sidestep Weapon's Safeguards
Having gotten a stolen nuclear weapon or nuclear material to their safe haven, the terrorist group would then have to attempt to prepare these items for use.
In the case of a stolen nuclear weapon, the weapon might well be equipped with some form of electronic lock (known in the United States as a permissive action link, or PAL) or other safeguards designed to prevent its use without authorization. Some older Russian weapons may still exist which are not equipped with such built-in safeguards, and some weapons from other countries may also lack these features. Older generations of such electronic locks can in principle be bypassed, effectively "hot-wiring" the weapon but figuring out how to do that would be a significant challenge for a terrorist group attempting to do it without help. More modern generations of such systems (on both U.S. and Russian weapons) are designed to permanently disable the weapon if there is an attempt to overcome the safeguard, posing an even more difficult hurdle, though no system is unbeatable. In some cases, a terrorist group might conclude that it would be easier to open the weapon, remove its nuclear material, and make a new bomb from that material.
In the case of nuclear material, the terrorist group would have to figure out how to make it into a bomb. Unfortunately, making a crude nuclear bomb is potentially within the capabilities of a sophisticated terrorist group though doing so would be perhaps the most technically challenging operation any terrorist group has ever undertaken.  A simple "gun-type" bomb, which slams two pieces of HEU together at high speed, would be much the easiest type of nuclear bomb for terrorists to construct, but such a weapon can only be made from HEU, and requires more of it (some 50 kilograms) than it would take to make a more efficient implosion bomb. An implosion bomb would be a significant technical challenge for a terrorist group though the possibility that a group such as al Qaeda might be able to acquire the expertise to meet that challenge cannot be ruled out.
One study by the now-defunct congressional Office of Technology Assessment summarized the threat: "A small group of people, none of whom have ever had access to the classified literature, could possibly design and build a crude nuclear explosive device... Only modest machine-shop facilities that could be contracted for without arousing suspicion would be required." 
Even before the Afghan war, U.S. intelligence concluded that "fabrication of at least a 'crude' nuclear device was within al-Qa'ida's capabilities, if it could obtain fissile material."  Documents later seized in Afghanistan provided "detailed and revealing" information about the progress of al Qaeda's nuclear efforts that had not been available before the war. 
The overthrow of the Taliban and the disruption of al Qaeda's old central command structure reduced the probability that al Qaeda would be able to pull off an operation as large and complex as acquiring nuclear bomb material and putting together a nuclear weapon. Unfortunately, however, as already noted, the latest intelligence assessments suggest that al Qaeda's central command is reconstituting its ability to direct complex operations, from the border areas of Pakistan.  As then-Director of National Intelligence John Negroponte put it in his annual threat assessment in January 2007, al Qaeda's "core leadership
continue to plot attacks against our Homeland and other targets with the objective of inflicting mass casualties. And they continue to maintain active connections and relationships that radiate outward from their leaders' secure hideout in Pakistan to affiliates throughout the Middle East, northern Africa, and Europe."  Unfortunately, the physics of the problem suggests that a terrorist cell of relatively modest size, with no large fixed facilities that would draw attention, might well be able to make a crude nuclear bomband the world might never know until it was too late.  (For more, see "Technical Background.")
Either for making a crude nuclear bomb or for figuring out how to set off a stolen nuclear weapon, having a haven where the work could be carried out without interruption would be quite important. While there are scenarios in which a terrorist group might be able to set off at least a modest-scale nuclear explosion with HEU relatively rapidly in essence, by simply driving two blocks of HEU together at high speed in most cases a substantial period of intensive, sustained work would be needed. In the case of an implosion bomb (the only type that can be made with plutonium, or with an amount of HEU too small for a gun-type bomb), an ability to test the explosive designs beforehand (using other commodities such as natural uranium as stand-ins for the plutonium or HEU that would eventually be in the core) would likely be very important. Al Qaeda had such a safe haven in Afghanistan, and may now be in the process of rebuilding a similar safe haven in the mountains of Pakistan. David Albright, who may well have studied more seized documents relating to al Qaeda's nuclear efforts than any other analyst, has concluded that al Qaeda "would have likely succeeded" in getting a nuclear bomb if the Afghan sanctuary had been maintained for several more years. Albright warns that while the risk has been reduced by the elimination of the Afghan sanctuary, it has not been eliminated, as al Qaeda is highly determined and may succeed in setting up unnoticed nuclear activities elsewhere. 
Having help from some one with experience in nuclear weapons design and manufacture (in the case of a stolen weapon, ideally some one familiar with the design of that weapon and its safeguards), would increase the chances of success substantially. Al Qaeda recognizes this, and has consistently attempted to recruit people with nuclear weapons expertise.  Former CIA chief Tenet, in his memoir, recounts his conversation with Pervez Musharraf, in which the Pakistani president assured Tenet that Pakistani nuclear experts had dismissed the possibility that "men hiding in caves" could build a nuclear bomb. "Mr. President, your experts are wrong," Tenet says he replied, recounting the relative ease of making a crude "gun-type" nuclear bomb, and al Qaeda's efforts to get help from Pakistani nuclear scientists associated with Ummah Tameer-i-Nau (UTN).  Osama bin Laden and his deputy Ayman al-Zawahiri met at length with two senior Pakistani nuclear weapons experts associated with UTN, Sultan Bashiruddin Mahmoud and Chaudari Abdul Majeed both Taliban sympathizers with extreme Islamic views and pressed them for information on making nuclear weapons. While Mahmoud and Majeed deny having supplied any useful information, Pakistani intelligence officials told the Washington Post that the two had provided detailed technical information, in violation of Pakistan's secrecy laws, in response to bin Laden's questions. 
Similarly, in 2000, an official of Russia's National Security Council announced that the Taliban regime had attempted to recruit a nuclear expert from a Russian facility  and in 1998, a scientist at one of Russia's premier nuclear weapons laboratories was arrested for spying for both the Taliban and Iraq (in this case on advanced conventional weapons designs, not nuclear weapons though the security services announced that this was by no means the first such espionage case at that laboratory). 
Here is where the threat reduction programs under the category of stabilizing employment for nuclear personnel, designed to keep weapons scientists and engineers employed in useful civilian work and thereby reduce the desperation that could create incentives to sell nuclear knowledge, have their greatest importance. At the same time, the United States and its partner countries should work with countries around the world to ensure that nuclear weapons experts are adequately paid, monitored, and controlled, with effective personnel reliability programs in place. Another important step would be to work with other nuclear states around the world to ensure that classified information related to nuclear weapons is adequately controlled, and to develop common guidelines on what information should stay secret and what information can be released so that those seeking nuclear weapons cannot piece key information together by combining facts inconsistently declassified by different countries. Finally, addressing some of the root causes of terrorism and anti-American hatred, and working to strengthen the moral taboo against the mass slaughter of civilians, may help make it more difficult for al Qaeda to recruit experts for a nuclear bomb program. 
Step 7: Smuggle Weapon Into Target Country
Once the terrorist group has figured out how to overcome whatever safeguards there may be on a stolen weapon, or figured out how to make a bomb of its own, the bomb must be smuggled into the target country. This could be done whole, or in pieces, with the idea of assembling the bomb at the target.
If the target country is the United States, the basic structure of the situation long borders, millions of people and vehicles crossing them, small size and low detectability of the bomb material again make preventing the smuggling an enormous challenge. U.S. borders remain extremely vulnerable to a wide range of possible smuggling.
Blocking this step in the terrorist pathway is the province of homeland security measures focused on better controlling U.S. borders (coupled with intelligence efforts that might receive a hint of where to look a key element throughout this pathway). The Department of Homeland Security is attempting to meet this daunting challenge, and a considerable amount of equipment to detect certain kinds of nuclear or radiological material has been installed at legal ports and border crossings into the United States since 9/11, along with some additional detection capabilities within the United States. Unfortunately, however, the possible means of bringing such a weapon into the United States are virtually unlimited: if a terrorist group was concerned that a bomb in a shipping container might be found, for example, they could put it in the hold of a yacht and sail it right up the Potomac or the Hudson, with no requirement to stop for inspection.
Step 8: Transport Weapon to Target Location
If the terrorist group has a particular target location in mind, beyond simply detonating the weapon as soon as it enters the target country, it will have to be transported to that location. Obvious possibilities would include the middle of Manhattan, as described above, the middle of Washington, D.C., or, for that matter, the center of any other major city.
Here again, the challenge of stopping such an operation is daunting, given the myriad ways that terrorists might choose to use and here again, it falls within the purview of homeland security efforts. Nuclear detectors of various types have been quietly installed at some points in some U.S. cities,  but it is not hard to imagine how these might be bypassed. If terrorists were concerned that major highways leading into their chosen target city might be equipped with some sort of detector, for example, they could either put some lead shielding around their bomb or carry it in by some other means for example by renting a modest-sized airplane and flying it over the city. The Nuclear Emergency Search Team (NEST), which has been deployed again and again since September 11, has considerable capabilities to search for and attempt to disable a nuclear device if they have specific information on where to look. But without such information, there would be little hope of finding a weapon.
Step 9: Detonate Weapon
Finally, if they had succeeded on each previous step of the pathway, the terrorists would detonate their bomb unleashing a terrifying holocaust of blast, fire, and radiation, as described above. The consequences of such an attack would be horrifying no matter what preparations had been made but improving plans for evacuation, treatment of the wounded, and decontamination could modestly reduce the consequences. 
Looking at this pathway, it is clear that the most effective countermeasures start with the early steps in the chain and particularly with preventing nuclear weapons and materials from being stolen in the first place. After such a theft, each of the later lines of defense is more desperate and more doubtful of success. Indeed, if defenses against nuclear weapons at the U.S. border or within the United States are ever called into play, this will represent a serious failure of U.S. policy, in failing to intercept the threat earlier in the terrorist pathway to the bomb. Hence, this report focuses on those programs intended to improve controls over nuclear weapons, materials, and expertise programs which offer the greatest leverage for keeping these items from falling into the hands of terrorists or hostile states.
Will states give terrorists the bomb?
In contrast to the urgent danger that terrorists might acquire a stolen nuclear weapon or stolen nuclear material, the probability that a hostile state such as Iraq would intentionally provide a nuclear weapon or the materials to make one to a terrorist group appears real, but small. 
Such a conscious decision by a nation-state to provide nuclear weapon capabilities to a terrorist group would effectively jump over the most difficult steps on the terrorist pathway to the bomb. In essence, all the terrorists would have to do is get the bomb to the target country and set it off.
The Defense Department's own most recent comprehensive assessment of the proliferation threat concludes that "the likelihood of a state sponsor providing such a weapon to a terrorist group is believed to be low."  There are several reasons why this is the case. First, a terrorist nuclear attack on the United States or one of its major allies and friends could be expected to provoke an overwhelming, devastating response. A state might hope that its transfer of such capability to a terrorist group would not be detected but it would be impossible to be sure it would not be, and the prospect of a retaliation that would destroy every remnant of the leadership of the state that provided the weapon would be very real. Before the U.S.-led invasion of Iraq, the CIA concluded, contrary to the prevailing rhetoric of the time, that Saddam Hussein was unlikely to attempt a WMD attack on the United States, or help a terrorist group with one unless he concluded that the United States was bent on destroying his regime no matter what he did, in which case "Saddam might decide that the extreme step of assisting Islamist terrorists in conducting a W.M.D. attack against the United States would be his last chance to exact vengeance by taking a large number of victims with him." 
Second, states hostile enough to even consider such an action are generally dictatorships ruled by men like Saddam Hussein and Kim Jong Il, men with an obsessive desire for control. Putting the most fearsome power they had ever acquired power that might be turned against them, or used in a way that would lead to unpredictable retaliation against them in the hands of a terrorist group they could not absolutely control would be contrary to the very nature of such leaders.
Third, nuclear weapons are extremely difficult for such states to acquire, and are regarded as the ultimate deterrent, and therefore the ultimate guarantor of regime survival. A hostile dictator is not likely to give away his ace in the hole to preserve his regime. (This argument is much less strong for chemical and biological weapons, for there, if a state can make enough for its own use, it is straightforward to make more to transfer to others.)
For all these reasons, it appears extremely unlikely that North Korea would provide nuclear weapons or the materials needed to make them to terrorist groups, despite its appalling record of marketing its conventional arms and missiles across the world. Putting such apocalyptic power in the hands of a group outside of the North's control would be fundamentally contrary to Pyongyang's desire to control every aspect of national life, and would be an immense gamble with the very future existence of the North Korean regime. Given that regime survival appears to be the highest goal of the Pyongyang government, this appears extremely unlikelyunless the regime concludes that its overthrow is inevitable or becomes so desperate that the revenue from a nuclear sale came to be seen as the only route to its survival. A decision by the Iranian government to provide nuclear weapons or materials to al Qaeda terrorists (in the future, when the Iranian government might have such items to provide) also appears extraordinarily unlikely, particularly as the Sunni al Qaeda has been sponsoring widespread attacks on Shiites in Iraq, Pakistan, and elsewhere. Nevertheless, the possibility of such transfers, however small, clearly highlights the urgency of putting together international packages of carrots and sticks large and credible enough to convince the North Korean and Iranian governments that it is in their national interests to verifiably abandon their nuclear weapons efforts.