Private search engines and traditional advertising platforms: uncovering the privacy risks

What is it about?

We investigate the privacy properties of the advertising systems employed by three major privacy focused search engines: DuckDuckGo, StartPage, and Qwant, and compare them with more widely used search engines: Bing and Google. We implement an automated measurement methodology to measure if and how users can be re-identified (hence, their privacy is compromised) when clicking on ads on each search engine. We apply this methodology to the five search engines and explore their privacy properties when (i) they present search ads to users, (ii) a user clicks on an ad, and (iii) the user lands on the advertiser's page.

Featured Image

Photo by Onur Binay on Unsplash

Photo by Onur Binay on Unsplash

Why is it important?

Several researchers and advocacy groups have condemned traditional search engines such as Google or Bing for the privacy-violating techniques they employ to deliver search results and ads to users. For example, these search engines use data from tracking users' information to estimate results' relevance and serve users with personalized ads. In response to these concerns, a number of private search engines such as DuckDuckGo, Startpage, and Qwant have emerged in the market. These private search engines promote a strategy of respecting user privacy and promise not to track users' search and browsing activities, all while delivering relevant search results. However, these private search engines rely on advertising for funding and can only maintain their commitment to privacy if they continue to deliver ads to their users. Alarmingly, they rely on traditional advertising systems that have been criticized for their lack of respect for users' privacy: DuckDuckGo and Qwant use Microsoft’s advertising system, while StartPage uses Google’s advertising system. Furthermore, when examining the privacy policies of these private search engines, we find that they are either silent or ambiguous on the privacy of the ads they deliver to users. Our results show that privacy-focused search engines' privacy protections do not sufficiently cover their advertising systems. Although these search engines refrain from identifying and tracking users and their ad clicks, the presence of ads from Google or Microsoft subjects users to the privacy-invasive practices performed by these two advertising platforms. When users click on ads on private search engines, they are often identified and tracked either by Google, Microsoft, or other third parties, through bounce tracking and UID smuggling techniques.