Annoyed Users: Ads and Ad-Block Usage in the Wild
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Annoyed Users: Ads and Ad-Block Usage in the Wild Enric Pujol Oliver Hohlfeld Anja Feldmann TU Berlin RWTH Aachen TU Berlin [email protected] [email protected] [email protected] ABSTRACT The history of this business model goes back to the first click- Content and services which are offered for free on the Internet are able Web ads, which emerged around 1993 with the first commer- primarily monetized through online advertisement. This business cial Web sites. HotWired was among the first to sell banner ads to model relies on the implicit agreement between content providers companies such as AT&T and Coors. The first central ad servers and users where viewing ads is the price for the “free” content. emerged in 1995 to enable the management, targeting, and track- This status quo is not acceptable to all users, however, as mani- ing of users and online ads. This started the proliferation of Web fested by the rise of ad-blocking plugins which are available for ads, which brought with it an increasingly complex infrastructure all popular Web browsers. Indeed, ad-blockers have the potential to serve these advertisements. DoubleClick introduced the process to substantially disrupt the widely established business model of of online behavioral advertising in the late 1990s which used 3rd “free” content—currently one of the core elements on which the party cookies to track users across sites and present ads based on the Web is built. users’ browsing patterns. Today, online advertisement has become In this work, we shed light on how users interact with ads. We a large and complex industry where entire exchanges trade user- show how to leverage the functionality of AdBlock Plus, one of the specific information for the purpose of better ad placements [58]. most popular ad-blockers to identify ad traffic from passive net- This user specific profiling has raised many privacy and secu- work measurements. We complement previous work, which fo- rity concerns in particular among privacy and consumer advocacy cuses on active measurements, by characterizing ad-traffic in the groups. The debate has, for instance, led to agreements about the wild, i.e., as seen in a residential broadband network of a major expiration dates of cookies as well as clear statements regarding the European ISP. Finally, we assess the prevalence of ad-blockers in collection of user information [8]. While the Federal Trade Com- this particular network and discuss possible implications for con- mission (FTC) identifies problems with online behavioral adver- tent providers and ISPs. tisement, it allows advertisers to continue this practice with some safeguards such as greater transparency, provisions for consumers to opt out, and special handling of sensitive data, e.g., those related Categories and Subject Descriptors to health and financial information [13]. The motivation underlying C.2.2 [Computer-Communication Networks]: Network Proto- the FTC’s position is that the FTC views online advertisements as cols; H.5.4 [Information Interfaces and Presentation]: Hyper- the key enabler for “free” content on the Web. text/Hypermedia However, to Web users, online advertisements can be perceived as being not only invasive to privacy, but also annoying, since they can distract them from the primary content they wish to consume. Keywords This situation has resulted in a proliferation of tools to evade or Web; Advertising; AdBlock Plus; Residential Broadband Traffic block the ads. We refer to these tools as ad-blockers. Among the most convenient and popular ad-blockers are extensions for Web browsers like Adblock Plus and Ghostery. According to Google 1. INTRODUCTION and Mozilla usage statistics of browser add-ons, Adblock Plus is The World Wide Web has fueled an unprecedented commercial- among the most popular. More than 30M users surf the Web daily ization of the Internet by turning a system designed for academic using a browser with this extension enabled [18, 15]. data exchange into a widely used social medium. The economic The use of ad-blockers is, however, perceived by the advertise- foundation of many services in this medium is online advertise- ment industry and content publishers as a growing threat to their ments (ads) which allow content and services to be offered free of business model [6, 19]. Their rationale is that ad-blockers provide charge to users. users a way to “evade paying” for the content they consume. Thus, some players try to put pressure on the developers of ad blocking Permission to make digital or hard copies of all or part of this work for personal or browser extensions in order to be excluded from the blocking. This classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation exclusion is envisioned to be implemented by i) removing them on the first page. Copyrights for components of this work owned by others than the from the filter lists, or ii) by adding them to a whitelist [6]. Others author(s) must be honored. Abstracting with credit is permitted. To copy otherwise, or also try to detect ad-blockers and explicitly appeal these users to republish, to post on servers or to redistribute to lists, requires prior specific permission either whitelist their site or completely disable the ad-blocker. and/or a fee. Request permissions from [email protected]. Another claim regarding the rise of ad-blockers is that “as more IMC’15, October 28–30, 2015, Tokyo, Japan. end users adopt them, revenues decline and the number of obnox- Copyright is held by the owner/author(s). Publication rights licensed to ACM. ACM 978-1-4503-3848-6/15/10 ...$15.00. ious advertisements increases” [3]. To break this vicious cycle DOI: http://dx.doi.org/10.1145/2815675.2815705. 93 some players in this domain encourage advertisers to adopt “ac- contrast to Ghostery, which is proprietary software, Privacy Bad- ceptable ads” as a compromise. The most important implication ger is open source—and based on Adblock Plus. Another option is of this initiative is that advertisements that conform to these guide- the NoScript plugin which is designed to interactively disable ex- lines are by default whitelisted by Adblock Plus [5], a setting that ecutable Web content such as JavaScript, which is often used by end users can still override. advertisers and trackers. Moreover, the ad-blocking debate is not uniquely centered on ad- To assess the popularity of these extensions we can refer to statis- blockers like Adblock Plus. In fact, some Internet Service Providers tics reported by popular browsers or to recent work by Metwalley (ISPs) have already stated their intention to block advertising on et al. [46]. They report, relying on a passive measurement study, their networks and thereby, force some companies in the advertis- that 80% of the households visible at their vantage point do not use ing business to share their revenues [12]. In light of this tussle be- any of these popular plugins. Among those that do, Adblock Plus tween users, advertisers, publishers, and ISPs, we inform the ongo- dominates, i.e., Adblock Plus is installed at 10%-18% of the house- ing debate with a passive measurement study about the “ad-scape” holds. Indeed, less than 3% of the households exhibit evidence of and how end users interact with it. other installed plugins. Given the popularity of Adblock Plus, we Our work: We complement previous work with a passive mea- next describe how this particular extension operates. surement study on advertisements. Namely, we collect traces from Adblock Plus. At the heart of Adblock Plus is the mechanism to fil- a residential broadband network (RBN) of a major European ISP to ter adverts based on filter rules that appear in filter lists. The regular i) elaborate on the prevalence of ad-blockers in this vantage point, expressions that form the set of filter rules follow a specific syntax, and ii) characterize ad traffic in the wild. The contributions of this which is described in detail in [4, 21]. If a filter rule matches a URL paper are as follows: that is not otherwise whitelisted, Adblock Plus will prevent the Web browser from requesting the URL. Hence, this extension reduces • We present a methodology to extract structural Web site in- network traffic as it averts undesired ad-related objects from being formation from packet header traces. With this methodology fetched. at hand, we can use the Adblock Plus functionality to classify However, some Web pages embed advertisements into the (main) ad traffic in passive measurements. We validate the effective- HTML document, e.g., textual advertisements. Since this docu- ness of this methodology with an active measurement study ment is required to render the page, the tool does not block the based on different configurations of an instrumented browser, download of these HTML documents. However, Adblock Plus in- e.g., running Adblock Plus. cludes functionality to hide such—otherwise displayed— embed- • We leverage two indicators to infer Adblock Plus usage: i) ded ads via CSS modification. Note that these ads are still trans- low ratio of ad requests, and ii) connections to the Adblock ferred over the network even though they will not be displayed in Plus servers. Based on these metrics we estimate that 22% of the browser to the user. the most active users likely use this extension. Moreover, we Filters Lists. Adblock Plus users can obtain various lists of filter have indications that, perhaps, most Adblock Plus users do rules via a subscription mechanism. There are several filter lists neither subscribe to EasyPrivacy (the list that protects them available for different purposes.