The Los Angeles Times takes a look at online privacy and data collected by marketing companies for programs such as targeted behavioral advertising.
Without letting you know, your Internet browser gulps down hundreds of the digital tracking beacons fed to it by the websites you visit, sometimes storing them for months or years, enabling an array of companies you’ve never heard of to monitor what you do online.
Cookies are not inherently dangerous — they are a kind of virtual ID card that helps browsers perform a number of online tasks that most users have come to expect: allowing you to stay logged in to your Google or Yahoo email service, or to go from page to page on Amazon.com while filling up your shopping basket with books. […]
But the useful cookies are far outnumbered by those that serve no other purpose than to keep track of what you do online. They often come from sites you have never visited. This can happen when you open pages that carry embedded advertisements, which are capable of adding cookies to your browser without your permission or knowledge — and often do.
These tracking cookies allow ad firms to follow you from site to site. Over time, the trail of sites you visit may allow them to build a demographic profile about you that includes your hobbies, place of residence, income level and even health status.
To get a sense of how many advertising companies have cookies on your computer, try visiting the Network Advertising Initiative, a cooperative of online ad companies. When you click on the “Consumer Opt Out” button, the NAI website will show you which of its member companies have tracking cookies on your browser.
You may be surprised to see your computer contains cookies from dozens of digital ad companies with names like Adblade, I-Behavior and ShareThis. The site gives you the option to opt out of tracking by these companies, which will neutralize the cookies’ ability to track you. But you should run this test frequently because the opt-out system is not legally binding or technically flawless, and over time, active cookies from these companies may start to reappear in your browser.