Optimal Welfare in Noncooperative Network Formation under Attack

TL;DR

This paper analyzes a game-theoretic model of decentralized network formation under attack, demonstrating that networks formed by selfish agents can achieve near-optimal welfare resilience against a broad class of attackers, improving previous bounds.

Contribution

It provides improved bounds on network robustness in a strategic setting and resolves an open problem regarding the welfare post-attack in decentralized networks.

Findings

Networks can resist large classes of attacks maintaining near-optimal welfare.

Counter-intuitively, attackers aiming to minimize social welfare do not cause the greatest damage.

The results improve existing bounds and demonstrate the resilience of selfishly formed networks.

Abstract

Communication networks are essential for our economy and our everyday lives. This makes them lucrative targets for attacks. Today, we see an ongoing battle between criminals that try to disrupt our key communication networks and security professionals that try to mitigate these attacks. However, today's networks, like the Internet or peer-to-peer networks among smart devices, are not controlled by a single authority, but instead consist of many independently administrated entities that are interconnected. Thus, both the decisions of how to interconnect and how to secure against potential attacks are taken in a decentralized way by selfish agents. This strategic setting, with agents that want to interconnect and potential attackers that want to disrupt the network, was captured via an influential game-theoretic model by Goyal, Jabbari, Kearns, Khanna, and Morgenstern (WINE 2016). We revisit this model and show improved tight bounds on the achieved robustness of networks created by selfish agents. As our main result, we show that such networks can resist attacks of a large class of potential attackers, i.e., these networks maintain asymptotically optimal welfare post attack. This improves several bounds and resolves an open problem. Along the way, we show the counter-intuitive result, that attackers that aim at minimizing the social welfare post attack do not actually inflict the greatest possible damage.