Rise of the incognito internet Safer surfing: protesters" use of identity protection software in the Arab uprisings of 2011 highlighted consumer interest in anti-tracking tools such as Ghostery Tim Dempsey found out his wife might be pregnant from a peculiar source: an online ad. "I was seeing adverts for pregnancy tests every time I turned on my laptop," says the 28-year-old executive. "I turned to my wife: "Is there something you're not telling me?" " She had been using his laptop to research pregnancy tests. This experience may become more common. Almost every action people take online is now monitored by a combination of "cookies," "beacons" and other such tracking devices. They are integral to online life, from timing how long web users spend on a website to remembering the items they put in their shopping baskets. Bec­ause of this, the browser now knows as much as about people's lives as they do - occasionally, as Mr Dempsey found, it knows more. The growth of such tracking devices has been rapid. In 1997, only a quarter of the world's 100 most popular websites had cookies installed. By 2011, they all did. Not surprisingly perhaps, software that covers people's tracks online is in­creasingly popular. For years, tools that blocked cookies and IP addresses were the preserve of the geeky few - now millions use them. "This situation reminds of what we saw in 2002 and 2003, when antivirus software took off with huge adoption," says Bill Kerrigan, chief executive at US company Abine, which makes DoNotTrackMe, software that blocks cookies and other tracking tools. It was this phenomenon of awareness that drove adoption. DoNotTrackMe has been downloaded 3m times since its launch in February. It is a trend seen at other anti-tracking companies. Ghostery, for example, a product that tells users what software a website is using to track them - and blocks it on request - has 40m active users around the world. "Our user base has changed significantly, with much more mainstream users," says Andy Kahl, director of consumer products at US-based Evidon, which owns Ghostery. Our biggest group of users now aren't that net-savvy - they shop online, have social networks, but aren't working in IT. The number of tracking devices used by websites has almost doubled in three years, according to the WebPrivacy Census, published by the Berkeley Center for Law and Technology at the University of California. The tools for monitoring users" activities are also increasingly sophisticated. In 2009 the 100 most popular sites - ranging from Google to CNN.com - used a total of more than 3,500 cookies to track visitors to their sites. Today that figure stands at just under 7,000. About a fifth of these sites use at least 100 cookies each. Retailers are among the most enthusiastic users of the technology. Just as retail chains watch how customers behave in a shop, online retailers monitor how long customers linger, where they arrive from and what they think about buying. In the UK, according to recent analysis by Ghostery, Play.com, which sells music and video games, had 76 tracking tags - more than any other big UK retailer. Amazon's UK website, meanwhile, used 43 trackers - fewer than the websites of Tesco, Debenhams or Marks and Spencer. When done openly, tracking is akin to a friendly shopkeeper, says Mr Kahl. If you go in every week, you're not concerned if a shopkeeper knows your regular order. Where that analogy breaks down is if you go across town to a different butcher's shop and he says: "Hi! I've got your steak and sausages."" Data collection should be a "transparent transaction," argues Lee Baker, until recently the head of the Association of Online Publishers, a trade body in the UK. I get my content for free, and you want some data? Great. Let's work that exchange. He adds that public understanding of how information is used is increasing. In the end, the consumer will become more aware of the value of their data. It is not just over-familiar retailers that consumers wish to hide from, however. "We saw hundreds of thousands come to our product due to the Arab spring," says Vernon Irvin, CEO at Virtual World Computing, which produces anti-tracking software called Cocoon, which he says has about 500,000 users to date. During anti- government uprisings last year activists used products such as Cocoon to try to sidestep government firewalls and monitoring, and to ac­cess social networks without detection. In Europe regulators are starting to crack down on how websites monitor users, which helps raise awareness of tracking. This year the EU brought in regulations forcing websites to ask visitors for consent to use cookies. At the same time, Microsoft introduced "do not track" as standard on its Internet Explorer web browser. The technology fires a request at websites not to use tracking technologies, and the move surprised and annoyed the ad­vertising industry - particularly as Internet Explorer accounts for about half of all internet users, by some measures. Google's Chrome browser followed with its own version of "do not track" in November. While these tools only request that websites do not track users - and can thus be ignored - they are "testament to the fact that privacy is going mainstream," says David Gorod­yansky, chief executive at US-based AnchorFree, a privacy app producer. People are becoming extremely aware and concerned about privacy. The app, which encrypts every web page a user visits, has been installed by more than 100m people. It is downloaded more than 1m times per week, while Mr Gorodyansky says revenues at the group have more than doubled year on year, although he declines to reveal figures. Anti-tracking companies say the market has potential to grow further. While users are more cautious about who might access their data and how it would be used, there is a still a big discrepancy between the precautions people take online compared to when leaving the house, says Mr Gorodyansky. Yet the consequences of surfing unprotected are potentially worse. "There is more data online than in people's homes," he says. While just over a third of digital data - such as private emails, or bank account details - should be kept secure, whether for regulatory or privacy purposes, only a fifth is, according the recent annual Digital Universe study, by research group IDC. Beyond security, however, what the bulk of users want is something very basic: privacy. The maxim of "nothing to hide, nothing to fear" should not apply, says Mr Irvin: "It doesn't mean I'm doing anything I don't want people to see. But, you know, I don't want people to know I have toenail fungus - and then toenail fungus ads to turn up everywhere.