Until now, efforts at preventing the proliferation of bioweapons have relied on limiting access to the pathogens themselves. However, if terrorists can produce a bioweapon from genome information alone, the same logic suggests that access to genetic information should also be restricted. Scientists have begun to discuss the restriction of the export of critical pieces of DNA. This measure could be extended to the three big genome databases. Scientists have long been aware of the potential dangers. The creation of polio, for instance, was forecast months ago in an essay in Nature Immunology pointing out that it would be simple to build an artificial polio virus. Nevertheless, most scientists still oppose any attempts to restrict access to information. Earlier this year, the US Department of Defense dropped proposals for checking any research it funds for “sensitive” information before it is published, after scientists protested that this would impede research needed to defend against bioweapons . This was the case with anthrax. Unlike some other potential bioweapons, anthrax still exists in nature, infecting animals and sometimes humans, and samples are held in many labs worldwide. There is no reason for a terrorist to try to recreate it. The same is not true of Ebola, smallpox or the 1918 flu virus. Even so, when the American Society for Microbiology considered whether it should publish the smallpox genome, it reasoned that the benefits in terms of understanding the virus and designing drugs outweighed the risks. Not all scientists share such views. Raymond Zilinskas of the Monterey Institute of International Studies in California thinks some limits should be placed on the publication of information on organisms such as smallpox. Zilinskas contends that most scientists feel that basic research should not be restricted in this fashion. But where does one cross the line? He and others have proposed that professional societies and editorial boards at scientific journals should exert more control. Even if they do not, the decision could be taken out of their hands. In addition to international measures, individual governments are also cracking down. The USA Patriot Act passed this year allows the federal government to stop some foreign nationals working in the US from getting access to certain pathogens and toxins. The US could extend this to cover access to genetic sequences as well.