### Abstract

Covert organizations are constantly faced with a tradeoff between secrecy and operational efficiency. Lindelauf, Borm and Hamers [13] developed a theoretical framework to determine optimal homogeneous networks taking the above mentioned considerations explicitly into account. In this paper this framework is put to the test by applying it to the 2002 Jemaah Islamiyah Bali bombing. It is found that most aspects of this covert network can be explained by the theoretical framework. Some interactions however provide a higher risk to the network than others. The theoretical framework on covert networks is extended to accommodate for such heterogeneous interactions. Given a network structure the optimal location of one risky interaction is established. It is shown that the pair of individuals in the organization that should conduct the interaction that presents the highest risk to the organization, is the pair that is the least connected to the remainder of the network. Furthermore, optimal networks given a single risky interaction are approximated and compared. When choosing among a path, star and ring graph it is found that for low order graphs the path graph is best. When increasing the order of graphs under consideration a transition occurs such that the star graph becomes best. It is found that the higher the risk a single interaction presents to the covert network the later this transition from path to star graph occurs.

Original language | English |
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Title of host publication | Mathematical Methods in Counterterorrism |

Editors | N. Menon, J.D. Farley, D.L. Hicks, T. Rosenorn |

Place of Publication | Vienna |

Publisher | Springer Verlag |

Pages | 215-228 |

Publication status | Published - 2009 |

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## Cite this

Lindelauf, R., Borm, P. E. M., & Hamers, H. J. M. (2009). On heterogeneous covert networks. In N. Menon, J. D. Farley, D. L. Hicks, & T. Rosenorn (Eds.),

*Mathematical Methods in Counterterorrism*(pp. 215-228). Springer Verlag.