GULYÁS, Gábor György, Ph.D.

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Know the price of your privacy!

2014-04-18 | Gabor

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We have discussed in our previous posts that companies track their users and the traffic on their website. Also there are companies offering solutions to track visitors. So the question is how much would you charge for a list of all the sites you visited in the past two weeks?  At a first glance, this might seem  a simple question. We have some surprising data for you!

In recent years the majority of websites adopted a business model in which you get a seemingly free service, but in exchange you give up your privacy. The model works simply: while you enjoy surfing freely, you are also being monitored and profiled in order to get advertisements and prices tailored to your interests. For example Orbitz steered Mac users to pricier hotels, this can also happen with you in other contexts, according how the advertisers estimate your affordability.

Auctions, where you are the product

When you open a website which has advertisements slots, there is the chance that your browsing history will be sold at an auction for advertisers, and your device will be involved in a real-time bidding (RTB) procedure. Do you remember our question in the previous section?

Have you considered your price?

Well, just to help positioning yourself, it is estimated that most of us would trade our privacy only in exchange of 7 EURs on average. Sounds nice, right? Unfortunately, this is just an unreal dream: our browsing history is being sold typicallyfor less than 0.0005 USD, as French researchers revealed in their recent study.

Who is making business  and how?

When you open a website that has its incomes from advertisements (for instance nytimes.com), a slot on their site can invoke an auction. Next, an ad exchange (e.g., DoubleClick or Facebook) will offer bidders to propose a price for placing their advertisements. The ad exchange identifies you with a tracking cookie (on nytimes.com), and distributes your browsing history among bidders, who will then have a chance to merge it with what they already know about you (tracked with another cookie). Thereafter, bidders have all the information to consider a price tag for you, and the bidder offering the highest price gets the chance to display the actual advertisement. This is a well-designed system, right? Also note that even loosing parties get a copy of your browsing history.

Price-tag sensitivity

Olejnik created tools with his collaborators to detect RTB and analyze winner prices. It may be impossible to get a global overview, as in many cases the winner prices are encrypted. Their analysis is based on the rest. It turns out that different visitor properties steer prices significantly. Location is one of the strongest factors, e.g., a profile located in the US had a price of 0.00069 USD, much higher than others located in France (0.00036 USD) or in Japan (0.00024 USD). They also discovered, that profiles are worth more in the morning. For instance, in their investigation a US profile was worth 0.00075 USD in the morning  and 0.00062 USD in the evening. Not surprisingly, browsing history also altered prices significantly. New profiles with no records are worth the least, while others with interesting history of visiting webshops (e.g., jewelry site) are worth more.

What can I do about this?

Using ad-blocks is only a partial solution. Use web bug killer instead. Web bugs are small programs advertisers use to detect user presence and to monitor activities. If you are a Firefox or a Ghostery user, you could use for instance Ghostery.

This post originally appeared in the Tresorit Blog.

Tags: web tracking, privacy, price of privacy, you are the product, tresorit blog

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