Analysis of Anthrax Bioterrorism in the United States Based on Open Source Information


Summary and Conclusions


The anthrax letter attacks against the United States were a tactical innovation in the use of biological warfare agents. While causing billions of dollars of damage, it nevertheless was not a mass casualty attack since only 5 people were killed and 17 sickened while over 30,000 were placed on prophylactic antibiotics.

These attacks were the first intentional use of highly refined Bacillus anthracis spores that were a dry powder and highly aerogenic. Despite conflicting evidence presented in open sources, the anthrax spores sent to Senators Daschle and Leahy were a highly developed product. Because their surface properties where modified in several different ways, it gave them the ability to become easily airborne without traditional dissemination devices. It is highly likely that the spore surface modification components were the products of a national level BW program with a significant history of research and development.

The common assertion that the attacks were a warning from a U.S. domestic source about the potential dangers of bioterrorism is rejected as not plausible. The most likely explanation of the intentions of the attackers was both a warning and demonstration of their capability. The nature of the warning message in the anthrax envelopes is consistent with Sunni Islamic extremist groups' interpretation of the Salafist religious principles, which require a warning with such an attack when it is not a ‘martyrdom operation’. Given the record of Al Qaida’s numerous declarations and public pronouncements, it is possible that this message was directed not only to the United States but to its Islamic followers in other countries as a show of strength.

Canada has had serious threats related to anthrax but it is unclear if there are any connections to the U.S. anthrax attacks. Fortunately, letters in Canada did not have the critical bacterial component. With respect to Canadian security, some key information about the spore preparations was released which may have a direct bearing on proliferation concerns related to anthrax weapons.


Introduction and Questions

While there are many descriptions of the main details of the anthrax attacks, several important questions remain unanswered. Given the sensitive nature of the circumstances and implications, it is likely that certain significant pieces of information will not be revealed. This report is an analysis of information available from open sources in order to attempt to answer the following questions:

  1. What were the intentions of the anthrax attacker(s)?
  2. Does the answer to question (1) give indications to the identity of the attackers or does it rule any potential groups out?
  3. Does the nature of the spore preparation give any information about the source of the spores?
  4. Can comparison of the U.S. anthrax attacks to any other anthrax incidents help assess the nature of these attacks?
  5. What are the connections and impact on Canadian security?



Statements to the public by the FBI indicate that the current working theory is that a domestic perpetrator was responsible for the attacks. Some commentators have made a case that the anthrax attacks were the work of a current or former scientist or contractor with ties to the U.S. Biodefense community. The intention of this person was to demonstrate the potential dangers of a bioterror attack to the U.S. Government and thereby increase defense expenditures or give increased emphasis to bioterror or WMD preparation. On the surface this may seem plausible but on closer examination it falls short.

Persons familiar with U.S. bioterror preparations would know that since 1994, U.S. government officials at the highest levels have been gravely concerned about countries such Iran, Iraq, North Korea and Syria that have developed or were in the process of developing WMD. As well these countries were known sponsors of terrorist groups. Within that problem, there was special concern about biological agents and their potential use for covert attacks. Examination of open source documents clearly demonstrates this trend right until the discovery of the first anthrax case in Florida, in October 2001.

The possibility of covert attacks with WMD weapons that caused mass casualties was the nightmare scenario that responsible officials had dreaded and drove many of their actions. In 1996 President Clinton signed a Presidential Directive directing a significant effort to counter these types of scenarios. The U.S. Department of Defense had made counterproliferation a top priority since 1994. Their objective was to deny, disrupt, delay and destroy WMD capabilities and their delivery systems of hostile countries or subnational groups.

Given the repeated declarations and rising concern related to WMD attacks, it is highly unlikely that a domestic anthrax attacker was trying to draw attention to the potential problem of bioterrorism.

Another argument that has been made that supports a domestic origin for the anthrax attacks concerns the strain of anthrax used in the attack. For example, Marilyn Thompson in her book on the anthrax attacks claims that the Ames strain has a ‘U.S. military’ origin and therefore supports a domestic origin for the attacks. However, it is known that this particular strain while used by the U.S. military for defensive testing has been widely exchanged. The Former Soviet Union’s biological weapons program had over 2000 strains of anthrax. For bacteria and virus strains in general, there was a free market especially before 1996. Until that time, there were over 60 international culture collections, which offered various strains of anthrax and other microorganisms for a nominal fee or exchange. After 1996, new restrictions in the U.S. limited these activities on select pathogens.

After nearly three years of investigation, there has been no reported evidence other than the envelopes, the threatening letters and bacterial contents of the letters. The official FBI investigation Amerithrax has been reported to be the largest investigation in FBI history. Clearly, an investigation of this sensitivity may preclude release of information that may adversely affect it. If it was a domestic criminal act, the chances are that the FBI would have made more progress in the case than it appears to have to date. Therefore, it appears it is unlikely to be a domestic crime.

Much of the debate in the open literature concerning the messages in the anthrax letters is based on the assumption that the letters cannot be taken at face value. The central argument is that violent Sunni Islamic extremist groups would never warn that anthrax spores were in the envelope. These arguments are a crucial misreading of Sunni Islamic extremist groups’ motives and methods. A fundamental part of their campaign is the numerous attempts to legitimize themselves as the true Islamic holy warriors and take on the mantle of a transnational Pan-Islamic movement. In 1998 Osama Bin Laden declared war on the United States and allies within a fatwa. The Sunni Islamic extremist groups put much effort in trying to justify their struggle in terms of their interpretation of Islamic principles. Again while many focus on the Wahabi influence on Al-Qaida, there are strong overtones of the Salafist tradition. Giving a warning may be consistent with this tradition. It should be remembered that the Sunni Islamic extremist groups have many ‘constituencies’ within many countries. It may have been a show of strength or a test to see the reaction of these supporters when they used biological agents.

In public testimony in 2002, the Director of Central Intelligence George Tenet stated that by 1998, Al Qaida had publicly declared its intentions to use CBRN weapons against the U.S. and its allies and that it was a ‘religious duty’ to acquire such weapons.

Therefore, the simplest explanation of the intentions, taking the letters included with the anthrax at face value, is also the most likely.

Nature of the Spore Preparations

Could the actions of the anthrax attackers be an example of tactical innovation in the use of high-grade anthrax spores? While causing billions of dollars of damage, it nevertheless was not a mass casualty attack since only 5 people were killed and 17 sickened while over 30,000 were placed on prophylactic antibiotics. The Laboratory Response Network in charge of bacterial testing performed over 150,000 tests for anthrax. It is reported that its personnel and technical capacity was stretched during those critical months in 2001. The widespread contamination of buildings clearly indicated that something was very special about the spores contained in some of those envelopes.

It was reported that Dr. Elisa Harris a former National Security Council official under President Clinton, said that she 'hoped that it was a U.S. scientist that mailed the anthrax since the alternative that foreign countries or groups could produce this grade of anthrax was even more troubling'. While it may be difficult to disagree with her reasoning, this highlights a critical point. The composition of the spores sent to Senators Daschle and Leahy had very special properties. It is the nature of these properties that has an important bearing on the subsequent analysis.

Dr. Alan Zelicoff of the Sandia National Laboratory was quoted as saying with respect to anthrax preparations which are dry, consist mainly of a single spore, and are surface charge modified to make them highly aerogenic, as the 'keys of the kingdom'. To clarify the significance, this refers to anthrax spore formulations with the following characteristics:

1) A concentration in the range of a trillion spores per gram;

2) high spore viability (greater than 90%);

3) monodisperse size distribution (greater than 80% in the size range of 1 to 5 micrometers); and,

4) chemical modification of spore surface and surface charge modified to enhance their air suspension time.

The implied danger of this kind of capability is that it would be an ideal anthrax weapon. The Dascle/Leahy anthrax had some of the characteristics of advanced treatments that suggest weaponization.

In the statements of people who developed biological weapons (most notably Ken Alibek and William Patrick) it was noted that it was not common to have an electrostatic charge on the spores from the former U.S. and Soviet Union's biological weapons programs. Furthermore, they stated that charges on the spores caused clumping and inefficient delivery. In fact, it may be a misconception that the presence of an electrostatic charge causes clumping. The main cause of clumping is short range molecular forces (called van der Waals forces) that only operate over tens of angstroms (one nanometers equals 10 angstroms). These are very small distances relative to spore size (roughly 10,000 angstroms or 1 micrometer). There is evidence that the attractive forces can be blocked effectively by adding a uniform coating of silica microspheres or nanoparticles. This results in a very different kind of anthrax spore, especially if an electrostatic charge is added by a second chemical modification. The spores now have two modifications - the net-like-charge causes the spores to mutually repel one another forming a spontaneous aerosol. As a secondary effect the charged particles adhere to lung alveoli more efficiently leading to increased infection. While there are disputes about whether the spores were modified as described above, it is clear from their dispersion patterns and characteristics that they were highly aerogenic.

The advanced additives and processes used to potentially weaponize the anthrax provide a several potential clues for scientific forensic evidence. Conceivably, it could be used to trace the spores to a specific laboratory that manufactured them. This assumes that there is access to the laboratory in question for comparison. The silica itself contains signature elemental impurities and morphological uniqueness that can allow identification of the manufacturer.

There is strong evidence that the surface properties may be a critical feature of the spore preparation. The surface charges of the spores were modified in a sophisticated way to both increases their tendency to get airborne and stay airborne. Spores that have the tendency to float in air rather than settle out will act like a gas which would greatly increase their ability to be inhaled by people and thus infect them.

Given the sophisticated nature of the surface spore modification and its apparent difference from past U.S. and Soviet Union anthrax weapons, the evidence points to biological weapons programs in other countries.

Comparison to other Anthrax Incidents

There are two important events that need to be considered. The first is the Sverdlovsk anthrax epidemic of 1979. The second was the attempts by the Japanese Aum Shinryko to disperse anthrax from the roof of their headquarters. There have been extensive reviews of both events, however my purpose is to compare salient facts in order to shed light on the anthrax bioterror attacks.

It was reported that about 100 people died from inhalation anthrax in April to May 1979 in Sverdlovsk in the former Soviet Union after a release of anthrax from a 'highly secured military facility'. Of course the Soviet officials denied the aerosol release and maintained that contaminated black market meat was to blame. It was only in 1992 after the breakup of Soviet Union, that Boris Yeltsin stated that it was an accidental release from a military facility.

After the sarin gas attacks, it was revealed that the Japanese cult Aum Shinryko tried several times to aerosolize liquid preparations of B. anthracis. They used an aerosol generator on the top of building. No injuries were reported from the spraying but people nearby complained of unusual odors coming from the cult headquarters.

Dr. Paul Keim of Northern Arizona University used DNA technology to show that the strain of anthrax bacteria used by Japanese cultists in the attempted biological attacks in 1993 was the non-virulent Sterne strain. This strain was obtained from a U.S. agricultural company, which sells it as a vaccine. As well, Dr. Keim showed that people who contracted anthrax in April 1979 in Sverdlovsk were infected with up to four different strains of B. anthracis bacteria. This does not occur naturally and corroborates the statement made by Boris Yeltsin that the anthrax outbreak was the result of an aerosol release from a government facility.

While the use of dry preparations of anthrax to contaminate large areas and kill people is a rare event, does the above information make it more likely that the anthrax used in the U.S. attacks was from a national biological weapons program? While it is more likely that the anthrax was from a national BW program, it gives no indication of which country could be the source. The FBI gave a 2-year window for the age of the anthrax spores used in 2001 based on carbon dating. During this time Iraq, Iran, North Korea and Syria had biological weapons programs as well as other countries.

Information on Al Qaida Biological programs

Information from the interrogation of senior Al Qaida members has been reported that has a bearing on the anthrax attacks and future biological programs. In late 2003, renewed concern about anthrax resulted from the questioning of senior al Qaida agents in U.S. custody. It was reported that after his arrest in March, Khalid Shaikh Mohammed, one of Al Qaida's top operatives, confirmed to U.S. officials that Al Qaida, and particularly its second in command, Ayman al- Zawahiri, an Egyptian physician, is attempting to or has acquired biological agents, particularly anthrax. There have been numerous confirmed reports that Al Qaida agents have inquired about renting crop-dusters. It was feared that their objective was to spread chemical or biological agents, especially anthrax.

Mohammed also revealed that until the U.S. attacks on Afganistan, Al Qaida's anthrax program was based in Kandahar, Afghanistan, and was led by two men: Riduan Isamuddin, known as Hambali, and Yazid Sufaat, a Malaysian member of Jemaah Islamiyah, an Al Qaida-affiliated group. Sufaat, who received a degree in biological sciences in 1987 from California State University at Sacramento, was a technician in the Malaysian military. Sufaat tried to acquire anthrax, but according to Hambali and Mohammed, Sufaat was not able to procure the Ames strain used in attacks. Other unconfirmed reports suggest that Sufaat was involved in obtaining anthrax samples from North Korea through the Moro Islamic Liberation Front for Al Qaida. Sufaat was arrested in 2001 as he tried to re-enter Malaysia. He has reportedly confirmed numerous details about Al Qaida's effort to develop anthrax and other biological agents. Hambali, who like Sufaat fled to neighboring Pakistan after the United States invaded Afghanistan has revealed some details about Al Qaida’s biological programs. He was arrested in Thailand and has been cooperating with U.S. officials. It was reported that Hambali had been trying to open a new biological weapons program for Al Qaida in the Far East when he was arrested.

Does any of this information preclude previous conclusions in this review? For example, if Hambali or Sufaat claim they did not possess the Ames strain but possibly had other strains of anthrax, this would suggest that their programs were not involved in the anthrax bioterror attacks. This supports information, which indicates that the capabilities of Sunni Islamic extremist groups lag their intentions with respect to anthrax bioterrorism.

In Bob Woodward’s book "Bush at War" George Tenet Director of Central Intelligence is quoted as saying, "I think its AQ" meaning Al Qaida. "I think there’s a state sponsor involved. It’s too well thought out, the powder’s too well refined. It might be Iraq, it might be Russia, it might be a renegade scientist," perhaps from Iraq or Russia.

While there has been much speculation about transfer of biological materials from countries that sponsor terror to terrorist groups, it is a difficult subject in terms of assessment. Clearly some matters cannot be resolved with open source information. It has pointed out that changes in the strategic environment may have led to less state-sponsored terrorism, but it has also made it better hidden when it does occur, because of the higher potential costs.

Relevance to Canadian Security

While Canada has had several anthrax threats, the most serious was a threatening letter sent to the Minister of Citizenship and Immigration on January 30, 2001. While the text of the message has not been revealed for security reasons, there are reports, of unknown reliability, that the letter was connected to Sunni Islamic extremist groups. Thus, Canada is not immune to these types of coercive threats whatever their source. The Canadian Government has taken actions to address these problems. This has included studies by DRDC Suffield to examine the spread of bacterial spores in closed environments with anthrax stimulants and potential countermeasures.

The Canadian Government has made efforts to counter proliferation of biological weapons a top priority. Information in the open literature concerning the anthrax attacks has revealed new levels of details related to the potential weaponization of anthrax spores. While many of the details are not explicit, certain key points, most notably information about the surface charge of anthrax spores, may provide clues to the weaponization process. In all likelihood, a sophisticated research and development program would still be needed to verify that the modified spores would work as intended.