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Privacy. Week 7 - February 28, March 2. Administrivia. Assign roles for class debate. Privacy policies. Policies let consumers know about site’s privacy practices Consumers can decide whether practices are acceptable, when to opt-out Presence increases consumer trust

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Week 7 - February 28, March 2

  • Assign roles for class debate
privacy policies
Privacy policies
  • Policies let consumers know about site’s privacy practices
  • Consumers can decide whether practices are acceptable, when to opt-out
  • Presence increases consumer trust
  • Make companies subject to FTC privacy-related enforcement
  • Rapid adoption 1998-2001*

* G.R. Milne and M.J. Culnan 2002. Using the Content of Online Privacy Notices to Inform Public Policy: A Longitudinal Analysis of the 1998-2002 US Web Surveys. The Information Society 18, 5, 245-359.

privacy policy problems
Privacy policy problems
  • BUT policies are often
    • difficult to understand
    • hard to find
    • take a long time to read
    • change without notice
privacy policy components
Identification of site, scope, contact info

Types of information collected

Including information about cookies

How information is used

Conditions under which information might be shared

Information about opt-in/opt-out

Information about access

Information about data retention policies

Information about seal programs

Security assurances

Children’s privacy

Privacy policy components

There is lots of informationto convey -- but policyshould be brief andeasy-to-read too!

What is opt-in? What is opt-out?

web privacy concerns
Web privacy concerns
  • Data is often collected silently
    • Web allows large quantities of data to be collected inexpensively and unobtrusively
  • Data from multiple sources may be merged
    • Non-identifiable information can become identifiable when merged
  • Data collected for business purposes may be used in civil and criminal proceedings
  • Users given no meaningful choice
    • Few sites offer alternatives
browser chatter
Browsers chatter about

IP address, domain name, organization,

Referring page

Platform: O/S, browser

What information is requested

URLs and search terms


To anyone who might be listening

End servers

System administrators

Internet Service Providers

Other third parties

Advertising networks

Anyone who might subpoena log files later

Browser Chatter
typical http request with cookie
Typical HTTP request with cookie

GET /retail/searchresults.asp?qu=beer HTTP/1.0


User-Agent: Mozilla/4.75 [en] (X11; U; NetBSD 1.5_ALPHA i386)


Accept: image/gif, image/jpeg, image/pjpeg, */*


Cookie:buycountry=us; dcLocName=Basket; dcCatID=6773; dcLocID=6773; dcAd=buybasket; loc=; parentLocName=Basket; parentLoc=6773; ShopperManager%2F=ShopperManager%2F=66FUQULL0QBT8MMTVSC5MMNKBJFWDVH7; Store=107; Category=0

referer log problems
Referer log problems
  • GET methods result in values in URL
  • These URLs are sent in the referer header to next host
  • Example:>index.html

  • Access log example
  • What are cookies?
  • What are people concerned about cookies?
  • What useful purposes do cookies serve?
cookies 101
Cookies 101
  • Cookies can be useful
    • Used like a staple to attach multiple parts of a form together
    • Used to identify you when you return to a web site so you don’t have to remember a password
    • Used to help web sites understand how people use them
  • Cookies can do unexpected things
    • Used to profile users and track their activities, especially across web sites
how cookies work the basics
How cookies work – the basics
  • A cookie stores a small string of characters
  • A web site asks your browser to “set” a cookie
  • Whenever you return to that site your browser sends the cookie back automatically

Please store cookie xyzzy

Here is cookie xyzzy





First visit to site

Later visits

how cookies work advanced
Cookies are only sent back to the “site” that set them – but this may be any host in domain

Sites setting cookies indicate path, domain, and expiration for cookies

Cookies can store user info or a database key that is used to look up user info – either way the cookie enables info to be linked to the current browsing session

How cookies work – advanced

Send me with requests for index.html on for this session only

Send me with any request to until 2008

DatabaseUsers …

Email …

Visits …




cookie terminology
Cookie terminology
  • Cookie Replay – sending a cookie back to a site
  • Session cookie – cookie replayed only during current browsing session
  • Persistent cookie – cookie replayed until expiration date
  • First-party cookie – cookie associated with the site the user requested
  • Third-party cookie – cookie associated with an image, ad, frame, or other content from a site with a different domain name that is embedded in the site the user requested
    • Browser interprets third-party cookie based on domain name, even if both domains are owned by the same company
web bugs
Web bugs
  • Invisible “images” (1-by-1 pixels, transparent) embedded in web pages and cause referer info and cookies to be transferred
  • Also called web beacons, clear gifs, tracker gifs,etc.
  • Work just like banner ads from ad networks, but you can’t see them unless you look at the code behind a web page
  • Also embedded in HTML formatted email messages, MS Word documents, etc.
  • For software to detect web bugs see:
how data can be linked
How data can be linked
  • Every time the same cookie is replayed to a site, the site may add information to the record associated with that cookie
    • Number of times you visit a link, time, date
    • What page you visit
    • What page you visited last
    • Information you type into a web form
  • If multiple cookies are replayed together, they are usually logged together, effectively linking their data
    • Narrow scoped cookie might get logged with broad scoped cookie
ad networks

search for medical information

buy CD

replay cookie

set cookie



Ad networks

Ad companycan get yourname and address fromCD order andlink them to your search

Search Service

CD Store

what ad networks may know
Personal data:

Email address

Full name

Mailing address (street, city, state, and Zip code)

Phone number

Transactional data:

Details of plane trips

Search phrases used at search engines

Health conditions

What ad networks may know…

“It was not necessary for me to click on the banner ads for information to be sent to DoubleClick servers.”

– Richard M. Smith

online and offline merging
Online and offline merging
  • In November 1999, DoubleClick purchased Abacus Direct, a company possessing detailed consumer profiles on more than 90% of US households.
  • In mid-February 2000 DoubleClick announced plans to merge “anonymous” online data with personal information obtained from offline databases
  • By the first week in March 2000 the plans were put on hold
    • Stock dropped from $125 (12/99) to $80 (03/00)
offline data goes online
Offline data goes online…

The Cranor family’s 25 most

frequentgrocerypurchases (sorted by nutritional value)!

  • Data on online activities is increasingly of interest in civil and criminal cases
  • The only way to avoid subpoenas is to not have data
  • In the US, your files on your computer in your home have much greater legal protection that your files stored on a server on the network
original idea behind p3p

P3P: Introduction

Original Idea behind P3P
  • A framework for automated privacy discussions
    • Web sites disclose their privacy practices in standard machine-readable formats
    • Web browsers automatically retrieve P3P privacy policies and compare them to users’ privacy preferences
    • Sites and browsers can then negotiate about privacy terms
p3p history

P3P: Introduction

P3P history
  • Idea discussed at November 1995 FTC meeting
  • Ad Hoc “Internet Privacy Working Group” convened to discuss the idea in Fall 1996
  • W3C began working on P3P in Summer 1997
    • Several working groups chartered with dozens of participants from industry, non-profits, academia, government
    • Numerous public working drafts issued, and feedback resulted in many changes
    • Early ideas about negotiation and agreement ultimately removed
    • Automatic data transfer added and then removed
    • Patent issue stalled progress, but ultimately became non-issue
  • P3P issued as official W3C Recommendation on April 16, 2002
p3p1 0 a first step

P3P: Introduction

P3P1.0 – A first step
  • Offers an easy way for web sites to communicate about their privacy policies in a standard machine-readable format
    • Can be deployed using existing web servers
  • This will enable the development of tools that:
    • Provide snapshots of sites’ policies
    • Compare policies with user preferences
    • Alert and advise the user
the basics

P3P: Introduction

The basics
  • P3P provides a standard XML format that web sites use to encode their privacy policies
  • Sites also provide XML “policy reference files” to indicate which policy applies to which part of the site
  • Sites can optionally provide a “compact policy” by configuring their servers to issue a special P3P header when cookies are set
  • No special server software required
  • User software to read P3P policies called a “P3P user agent”
what s in a p3p policy

P3P: Enabling your web site – overview and options

What’s in a P3P policy?
  • Name and contact information for site
  • The kind of access provided
  • Mechanisms for resolving privacy disputes
  • The kinds of data collected
  • How collected data is used, and whether individuals can opt-in or opt-out of any of these uses
  • Whether/when data may be shared and whether there is opt-in or opt-out
  • Data retention policy
p3p xml encoding

P3P version

Location ofhuman-readableprivacy policy

P3P policy name

Site’s nameandcontactinfo

Access disclosure


How data maybe used


Data recipients

Data retention policy

Types of data collected

P3P/XML encoding

<POLICIES xmlns="">

<POLICY discuri=""










<DATA ref="">Web Privacy With P3P</DATA>





<CONSEQUENCE>We keep standard web server logs.</CONSEQUENCE>





<DATA ref="#dynamic.clickstream"/>

<DATA ref="#dynamic.http"/>





p3p1 0 spec defines

P3P: Introduction

P3P1.0 Spec Defines
  • A standard vocabulary for describing set of uses, recipients, data categories, and other privacy disclosures
  • A standard schema for data a Web site may wish to collect (base data schema)
  • An XML format for expressing a privacy policy in a machine readable way
  • A means of associating privacy policies with Web pages or sites
  • A protocol for transporting P3P policies over HTTP
a simple http transaction

P3P: Introduction

GET /index.html HTTP/1.1


. . . Request web page

HTTP/1.1 200 OK

Content-Type: text/html

. . . Send web page

A simple HTTP transaction


with p3p 1 0 added

P3P: Introduction

GET /w3c/p3p.xml HTTP/1.1


Request Policy Reference File

Send Policy Reference File

Request P3P Policy

Send P3P Policy

GET /index.html HTTP/1.1


. . . Request web page

HTTP/1.1 200 OK

Content-Type: text/html

. . . Send web page

… with P3P 1.0 added



P3P: Introduction

  • P3P clients can check a privacy policy each time it changes
  • P3P clients can check privacy policies on all objects in a web page, including ads and invisible images|2|68523|1|146|ADFORCE

p3p in ie6

P3P: Introduction

P3P in IE6

Automatic processing of compact policies only;

third-party cookies without compact policies blocked by default

Privacy icon on status bar indicates that a cookie has been blocked – pop-up appears the first time the privacy icon appears


P3P: Introduction

Users can click on privacy icon forlist of cookies; privacy summariesare available atsites that are P3P-enabled


P3P: Introduction

Privacy summary report isgenerated automaticallyfrom full P3P policy

p3p in netscape 7

P3P: Introduction

P3P in Netscape 7

Preview version similar to IE6, focusing, on cookies; cookies without compact policies (both first-party and third-party) are “flagged” rather than blocked by default

Indicates flagged cookie


P3P: Introduction

Users can view English translation of (part of) compact policy in Cookie Manager


P3P: Introduction

A policy summary can be generated automatically from full P3P policy

privacy bird
Privacy Bird
  • Free download of beta from
    • Origninally developed at AT&T Labs
    • Released as open source
  • “Browser helper object” for IE6
  • Reads P3P policies at all P3P-enabled sites automatically
  • Bird icon at top of browser window indicates whether site matches user’s privacy preferences
  • Clicking on bird icon gives more information
privacy finder
Privacy Finder
  • Prototype developed at AT&T Labs, improved and deployed by CUPS
  • Uses Google or Yahoo! API to retrieve search results
  • Checks each result for P3P policy
  • Evaluates P3P policy against user’s preferences
  • Reorders search results
  • Composes search result page with privacy annotations next to each P3P-enabled result
  • Users can retrieve “Privacy Report” similar to Privacy Bird policy summary
is privacy finder useful
Is Privacy Finder useful?
  • Do users care about web site privacy?
  • Have enough web sites adopted P3P that typical search results contain sites with P3P policies?
    • Do users have meaningful choices among privacy policies?
  • Do users understand information provided by Privacy Finder?
  • Does Privacy Finder influence online purchasing decisions?
have enough sites adopted p3p
Have enough sites adopted P3P?
  • We weren’t sure, so we did a study….
    • Draft paper at
  • Previous studies examined lists of “most popular” web sites for P3P adoption, but this gives incomplete picture
  • Compiled two lists of search terms:
    • Typical: 20,000 terms randomly sampled from one week of AOL user search queries
    • Ecommerce: 940 terms screen scraped from Froogle front page
  • Submitted search terms to Google, Yahoo!, and AOL search engines and collected top 20 results for each term
  • Checked each result for P3P policy and evaluated policies against 5 “rulesets” and P3P validator
  • Saved 1,232,955 annotated search results in database
  • Separately checked for P3P policies on 30,000 domains most clicked on by AOL search engine users
results p3p deployment
10% of results from typical search terms have P3P

21% of results from ecommerce search terms have P3P

More popular sites are more likely to have P3P

5% of sites in our cache have P3P

9% of 30K most clicked on domains have P3P

17% of clicks to 30K most clicked on domains have P3P

Results: P3P deployment

% of domains with P3P policies

Most clicked on domains

results most popular p3p policies
Typical Terms

Ecommerce Terms

Results: Most popular P3P policies
results frequency of p3p enabled hits
Results: Frequency of P3P-enabled hits
  • 83% of searches had at least one P3P-enabled site in top 20 results
  • 68% of searches had at least one P3P-enabled site in top 10 results
  • For top 20 search results returned by AOL search engine for typical search terms:
    • 29% return at least 1 P3P-enabled hit that matches medium privacy preferences
    • 34% return at least 1 P3P-enabled hit in that does not share data
    • 31% return at least 1 P3P-enabled hit that does not market without opt-in
    • Thus, ~ 1/3 of the time AOL users will find site with “good” privacy policy in first 2 pages of results
does privacy finder influence purchases
Does Privacy Finder influence purchases?
  • Studies begun and more planned….
    • Pay users to make online purchases with their own credit cards
    • Some will use Privacy Finder and some will use generic search engine
    • Experiment with more and less privacy-sensitive purchases
    • Experiment with price-sensitivity
  • We’re just finishing initial study of 24 college students purchasing power strips and condoms
why web sites adopt p3p

P3P: Introduction

Why web sites adopt P3P
  • Demonstrate corporate leadership on privacy issues
    • Show customers they respect their privacy
    • Demonstrate to regulators that industry is taking voluntary steps to address consumer privacy concerns
  • Distinguish brand as privacy friendly
  • Prevent IE6 from blocking their cookies
  • Anticipation that consumers will soon come to expect P3P on all web sites
  • Individuals who run sites value personal privacy
p3p early adopters

P3P: Introduction

P3P early adopters
  • News and information sites – CNET,, BusinessWeek
  • Search engines – Yahoo, Lycos
  • Ad networks – DoubleClick, Avenue A
  • Telecom companies – AT&T
  • Financial institutions – Fidelity
  • Computer hardware and software vendors – IBM, Dell, Microsoft, McAfee
  • Retail stores – Fortunoff, Ritz Camera
  • Government agencies – FTC, Dept. of Commerce, Ontario Information and Privacy Commissioner
  • Non-profits - CDT

P3P: The future

  • Some companies that P3P-enable think about privacy in new ways and change their practices
    • Systematic assessment of privacy practices
    • Concrete disclosures – less wiggle room
    • Disclosures about areas previously not discussed in privacy policy
  • Hopefully we will see greater transparency, more informed consumers, and ultimately better privacy policies
evaluating information sources

Research and Communication Skills

Evaluating information sources
  • Don’t believe everything you read!
  • News sources are usually a reporter's interpretation of what someone else did
  • Conference and journal papers are first hand reports of research studies that have been peer reviewed
    • but journals usually have more review than conferences
  • Technical reports are usually first hand reports of research studies that have not been peer reviewed (yet)
    • Look for subsequent conference or journal publications
  • Web sites and books are anything goes, but books at least have an editor (usually)
  • When possible, cite research results and technical information from peer reviewed sources