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Understanding CalOPPA’s “Do Not Track” requirement

Disclose how the operator responds to Web browser “do not track” signals or other mechanisms that provide consumers the ability to exercise choice regarding the collection of personally identifiable information about an individual consumer’s online activities over time and across third-party Web sites or online services, if the operator engages in that collection. Disclose whether other parties may collect personally identifiable information about an individual consumer’s online activities over time and across different Web sites when a consumer uses the operator’s Web site or service. Though these requirements sound straightforward, in practice it can be difficult to determine which activities trigger the law’s disclosure requirement. This problem is compounded by the law’s loose relationship to the W3C Web Tracking Protection specification, the draft technology standard that established the “Do Not Track” mechanism and instigated the CalOPPA amendment. That specification, which has not yet graduated into a final standard, also attempts to define what kinds of tracking are acceptable and how they should be disclosed to users, but CalOPPA’s requirements do not map directly to the specification’s. This article is intended to serve as a practical guide to applying CalOPPA, grounded in the technology and policy behind Do Not Track.

How web requests work

To understand how users are tracked online and how the Do Not Track mechanism addresses the issue, it’s helpful to understand the basics about how web browsers interact with websites. When a user navigates to a website using a browser, the browser sends an HTTP request to the website’s server that looks something like this:

GET /index.html HTTP/1.1

The server then sends back a response in a similar format. If the request was successful, the server will provide the page requested, in the form of a text file in HTML format. The server can also instruct the browser in its response to store a cookie, i.e. a small text file provided by the server, on the user’s computer. The HTML file provided by the server will typically contain links to other files on the web server—including images files, stylesheets, and javascript code—which provide some of the page’s content, formatting, and functionality. For each of these linked resources, the browser sends an additional HTTP request and receives a corresponding response like those above. The browser then renders the web page by assembling all of these pieces as instructed by the HTML file. Most modern websites also include resources from third-party sites. For example, a page might embed an Instagram image or a Facebook “Like” button, or some javascript that allows the operator to monitor user interactions with Google Analytics. The browser will retrieve these in the same way, by sending HTTP requests to the third-party servers that hosts them. Those servers provide the content directly to the browser, and may also instruct the browser to store cookies. This all goes on in the background—the user may never see that his or her browser connected to these third-party services.

Privacy concerns around tracking

When we refer to “tracking” online, we might be talking about any number of activies, ranging from the commonplace and benign to the creepy or predatory. On the benign end of that range are things like:
  • The use of session cookies to keep track of a user’s activity over the course of a single visit to a website, for example to maintain a “shopping cart” for users who are not logged in.
  • The short-term logging of visitors’ IP addresses, to identify abusive activity (e.g. denial-of-service attacks) or troubleshoot technical issues.
These are not what most users have in mind when they object to being tracked online. More often, they’re picturing a faceless marketing company, secretly logging information about their shopping and browsing habits, compiling a comprehensive profile on them, and selling that information to advertisers, insurance companies, and others without their knowledge or consent. While there are undoubtedly companies doing all of these things, the majority of online tracking falls short of this extreme. Advertising and analytics services do collect extensive records of users’ online behavior, but often this data is not associated with users’ PII (apart from their IP addresses). These services collect user information primarily through websites that embed their content. If a website uses Google Adwords to display contextual ads to users, then every time a visitor accesses that site, their browser also accesses Google’s servers to request the javascript that enables the ads. This request tells Google the user’s IP address and which page the user is accessing. It also permits Google to access any cookies it has previously stored in the user’s browser and to store new cookies, unless the user has configured his or her browser to reject cookies. Google can then associate this information with information it has kept about previous visits, using the visitor’s IP address or another unique identifier stored in a cookie to link information about different visits together. This kind of tracking activity is pervasive: social sharing tools, embedded images, and web analytics services all track user behavior in much the same way, and most websites employ one or more of them. Though less problematic than the worst-case scenario discussed above, these activities raise a number of privacy issues: contextual ads can implicitly reveal past browsing behavior to others against users’ wishes; advertisers can be hacked, and their records of user behavior deanonymized and used for malicious purposes; and poor security practices on the part of website operators can cause PII to be leaked to advertisers.

The Do Not Track signal

The Do Not Track signal is a browser option that indicates that the browser’s user wishes not to be tracked. When the browser sends an HTTP request to a website, the user’s Do Not Track preference is communicated as part of the request. A request containing a Do Not Track header looks something like this:

GET /index.html HTTP/1.1
DNT: 1

Here, the Do No Track (DNT) signal is “on,” meaning the user requests not to be tracked. But an HTTP request is just that: a request. How the web server responds to the request, including the Do Not Track header, depends on how it’s configured. Right now, most websites probably are not configured to respond to Do Not Track headers at all, largely because the technical standard that is supposed to determine how they should respond has not been finalized. CalOPPA accounts for this uncertainty by limiting its requirements to disclosure: operators need not respond to Do Not Track signals in any particular way, but they must tell users how they respond. But without a final standard to navigate by, even this requirement puts operators in a difficult position. Should they create comprehensive Do Not Track policies and configure their systems to implement them—a potentially resource-intensive process for many sites—despite the risk that the final standard will vary significantly from the current draft? Should they wait for the final standard and, in the meantime, comply with CalOPPA by simply stating in their privacy policies: “This site does not respond to Do Not Track signals”? Many sites are opting for the latter, but to those unfamiliar with the law, a statement like this can make it look like the site is flouting privacy concerns. In a recent article questioning the privacy claims of secret-sharing websites Whisper and Secret, for example, Wired pointed out that “Secret even admits in its privacy policy that its website ignores the advertising industry’s ‘do not track’ option built into browsers.” CalOPPA’s definition of “tracking” also differs from the W3C specification’s. CalOPPA requires operators to disclose how they respond to Do Not Track if they engage in “the collection of personally identifiable information about an individual consumer’s online activities over time and across third-party Web sites or online services.” The specification, on the other hand, permits operators to track user activity over time—even if they’ve requested not to be tracked—so long as the operator does not share information about the users’ interactions with third parties. Thus, an operator that does not share data with third parties can comply with the specification without altering its behavior in response to Do Not Track signals, but may still be required by CalOPPA to notify users that it does not respond to Do Not Track signals.

Implementing the W3C Specification

Despite the unfinished state of the W3C specification, some operators will prefer to implement it rather than tell users that their Do Not Track preferences will be ignored. The specification has two sets of requirements: those that apply to “first party” websites and those that apply to “third party” websites. The first party is the site a user primarily intends to interact with—for example, when a user accesses directly, by either entering “” in the browser’s location bar or clicking a link to, the first party is Google. If a user visits and that site displays ads provided by Google AdSense, the New York Times is the first party and Google is a third party. The first party’s basic obligation upon receiving a Do Not Track signal is simple: do not share information about the user’s visit with third parties. As long as the operator only uses the information internally, the specification places no limits on the information it may collect. If the first party engages a service provider to assist in processing the user’s data, but that provider is bound by contract not to share the data or use it for any other purpose, sharing with that service providers is not restricted regardless of the user’s Do Not Track preference. A third party to the user’s visit may only:
  • collect, share, or use data related to that interaction; or
  • use data about previous network interactions in which it was a third party
if one of the following applies:
  • the user has explicitly consented to the collection, sharing, or use;
  • the data is collected for one of several limited “permitted uses”—frequency capping, financial logging, security, debugging, or audience measurement—and subject to certain limitations; or
  • the data is de-identified according to the procedure defined in the specification.
Each party to a given user interaction is responsible only for its own compliance. The first party is not required to police the collection of third parties whose sites are accessed in the course of the user’s visit. Therefore, a site that receives a Do Not Track signal from a user would not be required to remove contextual advertising or social sharing buttons from pages served to that user; it would be the obligation of the sites providing those resources to respond appropriately to the user’s Do Not Track preference. So when would an operator be required to change its behavior upon receiving a Do Not Track signal from a visitor? One example involves the relatively common practice of trading customer lists to marketing companies for access to more extensive mailing lists or other marketing channels. (The practices of these so-called “data brokers” are described in detail in a 2013 report published by the Federal Trade Commission.) Under the W3C specification, website operators would be prohibited from providing data brokers with any information obtained from visits in which the user’s Do Not Track preference was set to “on,” unless the user explicitly consented to the sharing or the information was de-identified. On a technical level, this would likely require flagging database records or segregating log entries corresponding to Do Not Track-restricted activity to ensure that those records are not shared with data brokers. The complexity of implementing these measures will vary with the details of each operator’s technical infrastructure. Most operators will need to make operational as well as technical changes to implement Do Not Track compliance. For example, marketing staff may need to training to identify flagged data and to avoid sharing it.


Compliance with CalOPPA’s Do Not Track disclosure requirement is a problem requiring customized solutions: every operator’s data-collection practices are different, so implementations will vary. Hopefully this guide shines a little more light on the requirements and how compliance works at a technical level. If you’d like further guidance on how to meet CalOPPA’s requirements, please get in touch.]]]]> ]]>

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