Advertising Fraud

Over the last decade, online advertising has become a major component of the Web, leading to large annual revenues (e.g., $26.04 billion in US in 2010 [4]). Internet advertising is a very successful form of advertising as it provides an easy and effective way for advertisements to be targeted to individual users’ interests. Unfortunately, fraudsters were able to exploit several vulnerabilities of the online advertising model and started abusing the system in order to make a profit out of it. These attacks are illegal only in a few countries and states (e.g., click fraud is a felony covered by Penal Code 502 in California and the computer misuse act in the UK). In most of the cases, the fraudsters instead violate terms of service of online advertising networks (e.g., in Nigeria where there is no law against this type of cybercrime and in India, where companies even advertised in national newspapers looking for people willing to use computers to click on ads, with no repercussions from authorities). In this chapter, we aim to provide a better understanding of vulnerabilities of online advertising systems, the well-known attacks, and possible countermeasures. We first address the online advertising system model and discuss different revenue models for it. We explain vulnerabilities of these models and classify the identified attacks into four main types: click fraud, malvertising, inflight modification of ad traffic, and adware. For each type of attack, we address how fraudsters can make profit from the existing advertising system. We discuss in more detail some of the attacks reported in practice. Finally, we address the possible countermeasures to each of the attacks. 1.1.1 Advertising on the Internet Online advertising is a form of marketing that relies on the Internet to deliver marketing messages to the targeted users. Internet advertisement typically comprises a short text, an image, or an animation embedded into a Web page. The purpose of an ad is generally to capture a user’s attention and persuade him to purchase or to consume a particular product or a service and, consequently, to increase the revenue of the advertiser. Advertisers pay for their ads to appear online, thus online advertising has become the major business model for monetizing online content. In contrast to other types of media (e.g., television or radio), online advertisements are not limited to an audience at a given time or a geographic location. An additional benefit is that online advertising allows for the customization of advertisements, thus increasing the probability that a user is interested in the advertised products and services. Hence, many advertisers, realizing the opportunities of online advertising, invest significant budgets into this form of advertising. Consequently, for many of the websites that users visit, a number of advertisements appear together with the content of a Web page. Now let us look at how online advertisements are embedded into the content of Web pages, which techniques are used to tailor ads to users’ interests and the main revenue models in online advertising.