Among several ways of trying to suppress terrorist conspiracies, infiltration has probably received the least attention. Impressionistic evidence suggests that conspiracies that carry out violent attacks usually have a small number of participants, and that large conspiracies either fail to materialize, fail to organize actual attacks, or are substantially less difficult to uncover. Due to the prevalence of weak social ties in larger groups there may be an intermediate group size, around 7-10 members, that is highly subject to infiltration. Building on work by Freeman, Granovetter, and others, this study examines a few features of the social ecology of interaction ties. We introduce a procedure for counting, within groups of size n, all interacting pairs {P, Q}, where P and Q are disjoint or nonoverlapping subsets (Freeman, 1992: 153) of a given group; these subsets usually contain more than one person, i.e., the interacting units do not invariably consist of individuals. This procedure generates interaction configurations having unique patterns of strong, weak, and "weakest" ties -i.e., three levels of tie strength corresponding to core, primary, and secondary ties in Freeman's terminology - such that relatively weak ties predominate within larger conspiracies. We speculate about ways in which these configurations may evolve through time. We then use a combinatorial analysis of group structure to develop a rough calculation of the probability of infiltrating conspiracies of size n, and we show that relatively large conspiracies, having 7 or more members, tend to have interaction structures that make them highly vulnerable to infiltration. Finally, Collins' (1985: 170-172) approach to interaction-chain analysis suggests that, while in real situations it would be hard to anticipate departures from our probability model, attempts to "turn around" conspirators with weak ties appear to have a fairly high prospect of success. - But the child's sob in the silence - Curses deeper than the strong man in his wrath. - Elizabeth Barrett Browning, "Cry of the children".
