A new digital arms race is looming. Users, advertisers, browser companies, and website owners are pitted against one another in a battle over online advertisements and the way individual consumer information is used to deliver targeted ads.

If not defused, escalation around these competing interests will create major problems for both individuals and the businesses that depend on the internet. The issue is coming to a head right now with a major Senate hearing today, new technology developments from browsers and advertisers, and a key meeting in the “Do Not Track” process the week after next.

What's the big deal? We expect to see ads for baby clothes and diapers when we visit an online maternity store. But some object to the practice known as “behavioral retargeting,” where the same ads follow us and show up on unrelated sites afterwards. Especially since the volume of cookies and other web tracking techniques has climbed sharply in recent years: According to a study last year led by Chris Hoofnagle and Ashkan Soltani, cookies were detected on the top 100 websites. They also found an average of 57 cookies per website and 100 or more cookies on one-fifth of the top websites.

Users should have a choice. Sounds simple enough. But it’s not.An overwhelming 87 percent of the overall cookies were set by third parties, rather than by the “first parties” users see when they first click or type a URL. Retargeting comes from such third-party advertising, because an advertising network typically places a cookie on our computers and then serves the baby clothes ads at one of the many other websites that participates in its network.

Given this growing online data collection, privacy groups, government regulators, and others have argued that users should have a choice. If people don't want to be tracked across multiple sites, then they should be able to indicate that choice through their browser settings: "Do Not Track."

Sounds simple enough.

But it's not. The devil lies in the details of implementation, for there are many stakeholders besides individual users in the online data collection and advertising ecosystem.

>Without effective targeting and tracking, ad revenue could plummet and lead to the shuttering of many popular websites.

Without effective targeting and tracking, advertisers argue, ad revenue could plummet and lead to the shuttering of many popular websites that rely on third party ads as their primary source of revenue. Those who buy and sell behavioral advertising and retargeting point out that advertising revenue supports the diverse array of free content available on the internet. From this perspective, online data collection enables innovative business models, and supports the long tail of smaller websites that get revenue from targeted advertisements.

Meanwhile, leading browsers have been competing against each other to offer stronger privacy protections, citing research that users would want a Do Not Track option if available. Last year, Microsoft decided it would turn the Do Not Track signal on by default. This spring, in a policy similar to one Apple had previously adopted, Mozilla announced that an upcoming version of its browser would block most cookies from third parties.

>The advertising industry claims this is a 'nuclear first strike.'

The advertising industry claims this is a "nuclear first strike" against them. And so begins the arms race, whereby the digital cookies currently used to track user habits are blocked by the browsers – only to have the advertisers respond with even more sophisticated tracking methods like digital fingerprinting. Browsers are gearing up to disable or reduce the effectiveness of such fingerprinting ... leading to yet another round of aggressive tracking tools by advertisers followed by blocking tools on the user side. And so on.

This sort of arms race would be bad for online sites and advertisers, as they would have to re-engineer their existing business models and enter an unstable period of measures and counter-measures between tracking and blocking. But it would be worst of all for end users, because existing websites wouldn’t function properly and current tools for managing user privacy through cookies would be broken.

#### Peter Swire ##### About The co-chair of the W3C Do Not Track standards process, Peter Swire is a law professor at Ohio State. He is also a former White House official who served in both the Clinton and Obama administrations on privacy and other technology issues.

So how do we scale back this looming escalation? The same way we defuse any other arms race: through negotiation.

Since late last year, I've co-chaired the Tracking Protection Working Group of the World Wide Web Consortium (W3C) – the same organization that created HTML and many other web standards. Tasked with developing a global Do Not Track standard, we've taken a multi-stakeholder approach that brings sharply different perspectives together at the discussion table: consumers, privacy groups, browser manufacturers, website owners, and various advertising and industry groups (all are well represented).

A negotiated Do Not Track standard offers the best way to avoid the arms race: It would allow individual users to indicate whether they wish to have personalized ads based on their surfing habits. It would allow websites and advertising networks to continue their existing cookie-based models with the consumers who don't opt out. And it would help avoid the sizzling controversy and escalation around cookie blocking and technical counter-measures.

Most importantly, it avoids the alternative: that the federal government imposes its own solution. Following today’s Do Not Track hearing called by Senator Rockefeller, an important Do Not Track meeting is scheduled for May 6 with all the major stakeholders on hand. If we don’t successfully negotiate a standard through the W3C process by then, there will be considerable pressure for other methods of solving internet problems.

In the meantime, we risk an unstable period for both individuals and industry. Surely an honorable and negotiated peace is better than a protracted arms race that breaks the World Wide Web?

Wired Opinion Editor: Sonal Chokshi @smc90