Deception in Social Learning

Abstract

A common assumption in the social learning literature is that agents exchange information in an unselfish manner. In this work, we consider the scenario where a subset of agents aims at deceiving the network, meaning they aim at driving the network beliefs to the wrong hypothesis. The adversaries are unaware of the true hypothesis. However, they will "blend in" by behaving similarly to the other agents and will manipulate the likelihood functions used in the belief update process to launch inferential attacks. We will characterize the conditions under which the network is misled. Then, we will explain that it is possible for such attacks to succeed by showing that strategies exist that can be adopted by the malicious agents for this purpose. We examine both situations in which the agents have access to information about the network model as well as the case in which they do not. For the first case, we show that there always exists a way to construct fake likelihood functions such that the network is deceived regardless of the true hypothesis. For the latter case, we formulate an optimization problem and investigate the performance of the derived attack strategy by establishing conditions under which the network is deceived. We illustrate the learning performance of the network in the aforementioned adversarial setting via simulations. In a nutshell, we clarify when and how a network is deceived in the context of non-Bayesian social learning.

Hidden Markov Modeling over Graphs

“…Repeatedly exchanging and fusing beliefs will allow the local information to diffuse throughout the network. Note that the proposed algorithm recovers standard loglinear social learning algorithms [14,15,16,17] when agents perform local Bayesian updates with γ = 1 and the true hypothesis is fixed:…”

“…First, each agent revises its belief via a Bayesian update based on new private data. Second, agents aggregate their neighbors' information into their beliefs with a distributed learning algo-rithm like consensus or diffusion [12,13,14,15,16,17]. A common assumption in these works is that the state of nature is fixed.…”