Itay Gonshorovitz Foundation of privacy Targeted Online Advertising.
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Transcript of Itay Gonshorovitz Foundation of privacy Targeted Online Advertising.
Itay GonshorovitzFoundation of privacy
Targeted Online Advertising
Topics
Introduction to online advertisement Understanding the participants and their
roles. Targeted advertising.
Privacy Issues Solutions
User based solutions Collaborative solutions
Conclusions
Introduction
Online Advertising plays a critically important role in the Internet world.
advertising is the main way of profiting from the Internet, the history of Internet advertising developed alongside the growth of the medium itself
Facts and short history
First internet banner, 1994, AT&T.
Also in 1994, the first commercial spam, a "Green Card Lottery".
The first ad server was developed by FocaLink Media Services and introduced on 1995.
In March 2008, Google acquired DoubleClick for US$3.1 billion in cash.
Parties Advertiser
Got money, wants publicity e.g., Coca-Cola
Publisher Got content, wants money Cnn.com
Ad-network Got advertising infrastructure, wants money e.g., Google AdSense, Yahoo
Consumer Wants free content
Business Model
CPM = Cost Per thousand impressions Impression: user just sees the ad. Rates vary from $0.25 to $100
CPC = Cost Per Click This is the cost charged to an
advertiser every time their ad is "clicked" on
Rates around 0.3$ per click
Click fraud
clicking on an ad for the purpose of generating a charge per click without having actual interest.
Might be: The publisher Advertiser’s competitor The publisher’s competitor
Ad-networks deal with it by trying to identify who clicks on the ads.
Online behavioral advertising
Online behavioral advertising refers to the practice of ad-networks tracking users across web sites in order to learn user interests and preferences.
Benefits Advertisers targets a more focused
audience which increases the effectively.
Consumer is “bothered” by more relevant and interesting ads.
How ad-networks match ads Most behavioral targeting systems work
by categorizing users into one or more audience segments.
Profiling users based on collected data Search history – analyzing search keywords Browse history - analyzing content of visited
pages Purchase history Social networks Geography
How Ad-Networks track users Cookies
3rd Party cookies Flash cookies
Web bug IP address User-agent Headers
Browser + OS More than 24,000 signatures
Levis.com case study
Privacy
Tracking and categorizing users by the ad-networks tend to violate user’s privacy.
The gathered information, linked with the users real identity, form a violation of privacy in its most basic form.
For example, if a person is searching the web for information on a serious genetic disease, that information can be collected and stored along with that consumer's other information - including information that can uniquely identify the consumer.
So… What we have so far?
User - Preserve his privacy Ad-Network & Publisher –
Maintain targeting and preserve their effectiveness and income
Still want to be able to fight click fraud Questions:
Do the two goals necessarily conflict? Or can they be both achieved?
Naive (paranoid) solution
Surf only across anonymizing proxies. TOR
Surf in private mode Advantages
Effective from the user’s perspective. Disadvantages
Are proxies really anonymizing? Very awkward Slower Damages targeted advertising
TrackMeNot (Howe, Nissenbaum, 2005)
Implemented as a Firefox plugin. Achieves privacy through obfuscation. Generates noisy queries. Starts with fixed a seed query list and
evolve queries base on previous results. Mimics user behavior so fake queries be
indistinguishable: Query timing Click through behavior
TrackMeNot
Advantages Simple
Disadvantages Still the real queries can be connected to
real identity. Might have problems with offensive
contents. Again, damages targeted advertising
Privad (Guha, Reznichenko, Tang , et al., 2009)
Require client software: saves locally database of ads (served
by the ad-network)
Learn user interests in order to match ads.
Match add from the local database according to the User interests.
Privad
Introduce new party – Dealer: Proxies anonymously all communication
between the user and the ad-network. might be government regulatory
agency. hides user’s identity from the ad-
network, but itself does not learn any profile information about the user since all messages between the user and ad-network are encrypted.
Privad
Advantages Ad-Networks can still target ads without
violates user privacy. Disadvantages
Complicated to add the new party. Ad-Network has to trust the dealer in order
to fight click-fraud which might unmotivated them to cooperate.
Adnostic (Toubina, Narayanan, Boneh, et al., 2009)
Two party solution: Client side: Implemented as a Firefox plugin. Server side: requires Ad-Network support
User’s preferences and interests are stored locally by the plugin, instead of at the Ad-network.
The targeted ad is selected by the plugin locally at the users computer, instead of at the Ad-Network servers.
Adnostic - Accounting
“charge per click” model remains unchanged.
“charge per impression” is harder. It uses homomorphic encryption scheme.
given the public key and ciphertexts , anyone can calculate
given the public key and ciphertexts , and scalar c, can be calculated.
Adnostic - charge per impression protocol
Client: Track user activity and maintains the data locally.
Visits an Ad supported website. Server: Sends a list of n ads ids along with
public key The browser chooses an ad to display to the
user. Then creates that matches the selected ad, then send , Along with zero-knowledge proof that and each is 0 or 1.
Adnostic - charge per impression protocol
Validates the proof. If the proof is valid then using homomorphic encryption calculates
when c is the price of viewing the ad. The server save encrypted counter for each ad and
add to it the previous values. Only one counter’s real value change.
At the end of the billing period, say a month, each counter is decrypted (should be done by trusted authority) and the advertisers pays for the ad-network.
Adnostic
Advantages Ad-networks can still target ads without
violates user privacy. Ad-networks can still detect click fraud
though it will be difficult without gathering information on IP even for a short time.
Disadvantages Ad-networks become weaker. Ad-networks can still track user if they are
willing to, and the protocol is built on trust.
Conclusions
In my opinion, It is hard to believe that ad-networks will give up the power of tracking users without legislation.
Nevertheless, There are reasonable solutions that still support targeted advertising without violating users privacy.
Questions?
References
[1] Daniel c. Howe and Helen Nissenbaum. Trackmenot: resisting surveillance in web search. 2005.
[2] Saikat Guha, Bin Cheng, Alexey Reznichenko, Hamed Haddadi, and Paul Francis. Privad: Rearchitecting online advertising for privacy. 2009.
[3] Vincent Toubiana, Arvind Narayanan Dan Boneh, Helen Nissenbaum, and Solon Barocas. Adnostic: Privacy preserving targeted advertising. 2009.
[4] Catherine Dwyer. Behavioral targeting: A case study
of consumer tracking on levis.com. In 15th Americas
Conference on Information Systems, 2009..