Annamaria Ficara et al. on Multilayer network analysis: the identification of key actors in a Sicilian Mafia operation

single-layer and multilayer social networks

EAI Fabulous 2021 proudly presents: the winning paper

EAI is proud to present the winning EAI Fabulous 2021 presentation as voted on by the conference attendees in the EAI Compass: Multilayer network analysis: the identification of key actors in a Sicilian Mafia operation by Annamaria Ficara (University of Palermo), Giacomo Fuimara, Pasquale De Meo, and Salvatore Catanese (University of Messina).

Annamaria Ficara’s best-voted paper on Multilayer network analysis: the identification of key actors in a Sicilian Mafia operation

Abstract. Recently, Social Network Analysis studies have led to an im- provement and to a generalization of existing tools to networks with multiple subsystems and layers of connectivity. These kind of networks are usually called multilayer networks. Multilayer networks in which each layer shares at least one node with some other layer in the network are called multiplex networks. Being a multiplex network does not require all nodes to exist on every layer. In this paper, we built a criminal multiplex network which concerns an anti-mafia operation called “Montagna” and it is based on the examination of a pre-trial detention order issued on March 14, 2007 by the judge for preliminary investigations of the Court of Messina (Sicily). “Montagna” focus on two Mafia families called “Mistretta” and “Batanesi” who infiltrated several economic activities including the public works in the north-eastern part of Sicily, through a cartel of entrepreneurs close to the Sicilian Mafia. Originally we derived two single-layer networks, the former capturing meetings between suspected individuals and the latter recording phone calls. But some networked systems can be better modeled by multilayer structures where the individual nodes develop relationships in multiple layers. For this reason we built a two-layer network from the single-layer ones. These two layers share 47 nodes. We followed three different approaches to measure the importance of nodes in multilayer networks using degree as descriptor. Our analysis can aid in the identification of key players in criminal networks.


During his lifetime, an individual continuously deals with multiple layers of social networks. A ‘traditional’ single-layer-perspective of social network analysis with nodes and edges can also be organized in multiple layers. The analysis of multiple layers can provide knowledge not present in each layer when layers are considered independently. 

The only multi-relational network about criminal relationships was described by Bright and his co-authors in 2015. A. Ficara and her co-authors propose a new multilayer criminal network derived from their previous works, where, using social network analysis tools as a way to deal with missing data, they could evaluate police interventions disrupting criminal networks.

Centrality is the most widely applied set of social network analysis tools in a practical context. In the background, given a set of nodes, the presence and the intensity of a relationship of two nodes can be indicated. Using multiple layers, one can represent different types of edges – the intra-layer and inter-layer edges. 

Background: Multilayer Networks

The Montagna Operation investigation focused on two mafia families infiltrating several economic activities. Based on the main data source – the pre-trial detention order by the preliminary investigation judge of the Messina court, The Meetings and Phone Calls Network graphs were built. The Dataset of a ‘multiplex’ two-layer network sharing 47 nodes between the two layers was created based on the simple Meetings and Phone Calls graphs, allowing to build the Aggregate Network ‘flattening’ – merging the two layers to obtain a single layer network. 

Using the multilayer network, it was possible to identify the two key regimes (nodes 25 and 61) of the Mistretta mafia family, as well as an associate (such as a pharmacist, node 43).

The structure of a Mafia Family

Using real criminal data obtained by passing pre-trial detention order by the court of Messina, Annamaria Ficara and her co-authors have built two data set-based social networks – one for meetings and one for phone calls between suspects with the layers of a multiplex network. Three different approaches: 1. The traditional degree is applied to each layer separately; 2. The traditional degree is applied to the aggregate network; 3. A new kind of degree produced merging the contributions of inter-layer edges in multiple layers, measuring the importance of nodes in the multiplex network using the degree as a descriptor, thus, identifying the top 20 actors of the Mafia Operation called Montagna. 


Annamaria Ficara is a PhD student at the Department of Mathematics and Computer Science at the University of Palermo. Her research topics include Social Network Analysis, Complex Networks, Network Science, Parallel Computing, and Centrality Measures.

EAI FABULOUS 2021, the 5th EAI International Conference on Future Access Enablers of Ubiquitous and Intelligent Infrastructures, was dedicated to the topic of Security of innovative services and infrastructure in traffic/transport/logistic ecosystem.

EAI Fabulous research conference

This small-scale but important research conference is dedicated to the exploration of various new concepts and paradigms in information and communication technologies. In concepts such as the Internet of Things, Cloud Computing, Big Data, or Artificial Intelligence, and in an ecosystem of interconnected elements and advanced communication between humans and machines, the challenge is to achieve and retain the required level of security and privacy. Thanks to the Fabulous conference, leading academic scientists, researchers, and research scholars can share their experiences and research results on all aspects of innovative and sustainable solutions for ubiquitous and intelligent communication infrastructures.