The apps way to tracking phone users
ONCE, only hairdressers and bartenders knew people's secrets. Now, smartphones know everything - where people go, what they search for, what they buy, what they do for fun and when they go to bed.
That is why advertisers, and tech firms like Google and Facebook, are finding new, sophisticated ways to track people on their phones and reach them with individualised ads.
Privacy advocates fear that consumers do not realise just how much of their private information is on their phones and how much is made vulnerable simply by downloading and using apps, searching the mobile Web or even just going about daily life using a phone.
And this new focus on tracking users through their devices and online habits comes against the backdrop of a spirited public debate on privacy and government surveillance.
Last Wednesday, the National Security Agency confirmed it had collected data from mobile-phone towers in 2010 and 2011 to locate Americans' mobile phones, though it said it never used the information.
"People don't understand tracking, whether it's on a browser or a mobile device, and don't have any visibility into the practices going on," said Ms Jennifer King, who studies privacy at the University of California, Berkeley, and has advised the Federal Trade Commission on mobile tracking.
"Even as a tech professional, it's often hard to disentangle what's happening."
Drawbridge is one of several start-ups that has figured out how to follow people without cookies, and to determine that a mobile phone, work computer, home computer and tablet belong to the same person, even if the devices are not connected.
Previously, logging onto a new device presented advertisers with a clean slate.
Mr Eric Rosenblum, chief operating officer at Drawbridge, said: "We're observing your behaviours and connecting your profile to mobile devices."
Drawbridge, founded by a former Google data scientist, said it has matched 1.5 billion devices this way, allowing it to deliver mobile ads based on websites the person has visited on a computer. If you research a Hawaiian vacation on your work desktop, you could see a Hawaii ad that night on your mobile phone.
For advertisers, intimate knowledge of users has long been the promise of mobile phones. But only now are numerous mobile-advertising services that most people have never heard of - like Drawbridge, Flurry, Velti and SessionM - exploiting that knowledge, largely based on monitoring the apps we use and the places we go to.
This makes it harder for mobile users to escape the gaze of private companies.
Ultimately, the tech giants, whose principal business is selling advertising, stand to gain. In the old days - just last year - digital advertisers relied mostly on cookies. But cookies do not attach to apps, which is why they do not work well on mobile phones and tablets.
Cookies generally work on mobile browsers, but do not follow people from a phone browser to a computer browser. The iPhone's mobile Safari browser blocks third-party cookies altogether. Even on PCs, cookies have lost much of their usefulness to advertisers, largely because of cookie blockers.
Responding to this problem, the Interactive Advertising Bureau started a group to explore the future of the cookie and alternatives, calling current online advertising "a lose-lose-lose situation for advertisers, consumers, publishers and platforms".
Most recently, Google began considering creating an anonymous identifier tied to its Chrome browser that could help target ads based on user Web-browsing history.
For many advertisers, cookies are becoming irrelevant as they want to reach people on mobile devices. Yet advertising on phones has its limits.
For example, advertisers have so far had no way of knowing whether an ad seen on a phone resulted in a visit to a website on a computer. They also have been unable to connect user profiles across devices or even on the same device, as users jump from the mobile Web to apps.
This is why a service that connects multiple devices with one user, such as Drawbridge, is so compelling to marketers.
Drawbridge watches the notifications for behavioural patterns and uses statistical modelling to determine the probability that several devices have the same owner and to assign that person an anonymous identifier.
Other companies, like Flurry, get to know people by the apps they use. Flurry embeds its software in 350,000 apps on 1.2 billion devices to help app developers track things like usage. Its tracking software appears on the phone automatically when people download those apps.