Community deception is about hiding a target community that wants to remain below the radar of community detection algorithms. The goal is to devise algorithms that, given a maximum number of updates (e.g., edge additions and removal), strive to find the best way to perform such updates in order to hide the target community inside the community structure found by a detection algorithm. So far, community deception has only been studied for undirected networks, although many real-world networks (e.g., Twitter) are directed. One way to overcome this problem would be to treat the network as undirected. However, this approach discards potentially helpful information in the edge directions (e.g., A follows B does not imply that B follows A). The aim of this paper is threefold. First, to give an account of the state-of-the-art community deception techniques in undirected networks underlying their peculiarities. Second, to investigate the community deception problem in directed networks and to show how deception techniques proposed for undirected networks should be modified and adapted to work on directed networks. Third, to evaluate deception techniques both in undirected and directed networks. Our experimental evaluation on a variety of (large) directed networks shows that techniques that work well for undirected networks fail short when directly applied to directed networks, thus underlying the need for specific approaches.

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Community deception is about protecting users of a community from being discovered by community detection algorithms. This paper stud- ies community deception in Directed Influence Networks (DIN) and aims to address limitations of the state-of-the-art through a two-fold strategy: introducing directed influence and considering the role of nodes in the deception strategy. The study focuses on using modularity as the optimization function and offers several contributions, including an upgraded version of modularity that accommodates the concept of influence, edge-based and node-based deception algorithms. The study concludes with a comparison of the proposed methods with the state-of-the-art showing that not only influence is a useful ingredient to devise deception strategies but also that novel deception strategies centered on node operations can be successfully devised.