worked with various foreign governments to suppress terrorism. While government research suggests personality traits that may be common to a substantial number of terrorists, terrorism has few other constants. It has taken place on every continent except Antarctica. In all these cases, intelligence support from the CIA was required. In some of them, clandestine intelligence collection and covert action by CIA personnel, or those they sponsored, dealt with terrorists and performed counter-terrorist roles. Many studies of the analysis of, and countermeasures to, terrorism remain classified. Declassified CIA documents on terrorism date back to the late 1970s. According to a 1979 report Western Europe often had opposing terrorist groups in the same conflict at that time, such as nationalists and separatists in Northern Ireland, Spanish nationalists and Basque separatists in Spain and others like them in Turkey. Transnational terrorism was still unusual, although the report noted that the Basque group ETA was active in France as well as Spain. There are relevant observations from government reports by researchers who have various levels of access into the IC, including the Federal Research Division (FRD) and Congressional Research Service of the Library of Congress. A 1999 FRD study examined some changes from terrorists of the past, especially the emergence of terrorist acts carried out by individuals and members of small, ad hoc groups largely unknown to security organizations. Tactics, as well as sources, had changed, with the greater use of suicide attacks and attacks by women and children. A very significant concern has been the possible use by terrorists of weapons of mass destruction (WMD). Tactics Suicide attacks Weapons of mass destruction Terrorists have already made multiple attacks using WMD, such as chemical attacks by Aum Shinrikyo. A 1996 CIA presentation reviewed the history to date, including Iraq's (now defunct) programs. Researchers for a 1999 General Accounting Office study had classified access, and concluded that terrorists could use some chemicals like chlorine with relative ease for an attack, while other agents, chemical and biological, would require greater sophistication. Collection approach HUMINT One of the biggest challenges in dealing with relatively small terrorist groups is that the members are usually known to one another, or at least there is a chain of individuals that can vouch for a recruit. These social bonds have led to the refinement of the clandestine cell system in such groups. The combination of familiarity and compartmentalization make it extremely