Online advertising has become the backbone of the Internet economy by revolutionizing business marketing. It provides a simple and efficient way for advertisers to display their advertisements to specific individual users, and over the last couple of years has contributed to an explosion in the income stream for several Web-based businesses. For example, Google’s income from advertising grew 51.6% between 2016 and 2018, to $\$ 136.8 billion. This exponential growth in advertising revenue has motivated fraudsters to exploit the weaknesses of the online advertising model to make money, and researchers to discover new security vulnerabilities in the model, to propose countermeasures and to forecast future trends in research. Motivated by these considerations, this paper presents a comprehensive review of the security threats to online advertising systems. We begin by introducing the motivation for online advertising system, explain how it differs from traditional advertising networks, introduce terminology, and define the current online advertising architecture. We then devise a comprehensive taxonomy of attacks on online advertising to raise awareness among researchers about the vulnerabilities of online advertising ecosystem. We discuss the limitations and effectiveness of the countermeasures that have been developed to secure entities in the advertising ecosystem against these attacks. To complete our work, we identify some open issues and outline some possible directions for future research towards improving security methods for online advertising systems.

中文翻译：

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在线广告安全：问题、分类和未来方向


在线广告彻底改变了商业营销，已成为互联网经济的支柱。它为广告商提供了一种简单而有效的方式来向特定的个人用户展示其广告，并且在过去几年中为一些基于网络的企业带来了收入流的爆炸式增长。例如，2016 年至 2018 年间，谷歌的广告收入增长了 51.6%，达到 1368 亿美元。广告收入的指数级增长促使欺诈者利用在线广告模型的弱点来赚钱，也促使研究人员发现模型中新的安全漏洞，提出对策并预测未来的研究趋势。出于这些考虑，本文对在线广告系统的安全威胁进行了全面回顾。我们首先介绍在线广告系统的动机，解释它与传统广告网络的区别，介绍术语，并定义当前的在线广告架构。然后，我们设计了在线广告攻击的全面分类法，以提高研究人员对在线广告生态系统漏洞的认识。我们讨论了为保护广告生态系统中的实体免受这些攻击而开发的对策的局限性和有效性。为了完成我们的工作，我们确定了一些悬而未决的问题，并概述了未来研究改进在线广告系统安全方法的一些可能方向。