The discovered node ncvt**, which is not labeled (named) in the figure, indicates the position where the wire-puller is most likely to conceal himself. The**
node has links (red broken lines) to the 4 neighbor nodes: Fayez Ahmed, Mohamed Atta, Marwan Al-Shehhi, and Waleed Alshehri. The neighbor nodes are nnbr ∈ d12, because dσ(0) = d12 **is the most suspicious intelligence data.**
Mohamed Atta and Waleed Alshehri hijacked the flight AA11, which flew into the North Tower of the World Trade Center. Mohamed Atta was the **leader of** the hijackers. Waleed Alshehri assisted Mohammed Atta. Fayez Ahmed and Marwan Al-Shehhi hijacked the flight UA175, which flew into the South Tower. Marwan Al-Shehhi, who trained at a pilot school with Mohammed Atta, **flew**
the aircraft. Fayez Ahmed was also a pilot. The wire-puller was a linkage between the 2 flights which were used as weapon to the financial landmark of the United States. They are the keystone neighbors to investigate to **unravel who** is the wire-puller, or what is behind the terrorist attack.

The ties between the persons concerned are revealed by [13]. They include the 19 perpetrators, conspirators, and suspects. The tie strength is estimated by the amount of time together by a pair of terrorists. Those living together, attending the same school, or the same training would have strong ties. Those traveling together, and participating in meetings together would have ties of moderate strength. Finally, those who were recorded as having a financial transaction together, or participating in an occasional meeting would have weak ties.

Publicly available data is used as such intelligence data set. By comparing with the ties in [13], the wire-puller in Figure 2 turns out to be Mustafa A. Al-Hisawi. He is believed to be a financial manager of Al Qaeda, and to give Fayez **Ahmed** a credit card as a financial support for the attack.

Remind that this result is for demonstration purpose. The objective is to demonstrate how the intuitive visualization can help the investigator **diagnose** the intelligence data set, rather than to uncover the real role of Mustafa A. Al-Hisawi, or Usama bin Laden in the 9/11 terrorist attack.

## 5 Conclusion

This paper presented a computational method to analyze the intelligence data set on the collective actions of the perpetrators of the terrorist **attack, and to visualize it into the form of a social network diagram, which predicts the positions**
where the wire-pullers conceals themselves. This will help the investigators, who have a limited time window to diagnose the organizational background **of the** terrorists, to run down and arrest the wire-pullers, and to take an action to prevent or eradicate the terrorist attack. The intuitive interface to visualize the intelligence data set will stimulate the investigators' experience and **knowledge,** and aids them in decision-making for an immediately effective action.

The important aspect of the presented method is that the diagnosis of the investigator illustrated in Figure 1 can be repeated many times. The investigator can predict the position of Mustafa A. Al-Hisawi from the intelligence **data set** on the 19 perpetrators. Then, once the wire-puller is identified as Mustafa A.