How to know who is tracking your Web activities
The free Ghostery add-on for Firefox, Internet Explorer, Google Chrome, Safari, and Opera tells you which third-party sites placed a tracking cookie in your browser when the current page opened and lets you block cookies selectively.
If there's one important feature missing from all the major browsers, it's the ability to know at a glance when you're being tracked, and with a single click by whom.
As I mentioned in my post on, a key source of revenue for Web services of all types is the sale of the Web activities of their users. Data about when people use their services and how they use them are recorded and anonymized (we hope).
Then ad networks serve people ads based on their Web habits. Unfortunately, the sites themselves don't always follow their own data-collection policies.
For example, Facebook was recording users' Web histories even after they had signed out of their Facebook account. The Electronic Frontier Foundation describes the glitch that caused the inadvertent data collection and Facebook's response, which pointed the finger at a defect in Facebook's cookie-management system--since corrected, we're assured.
Ghostery icon shows the number of trackers on the current page
After hearing about Facebook's overzealous tracking, I decided to take a two-week break from Facebook, just to see if I could stay off the company's radar screen for that long. I started by deleting all the cookies in Firefox and Google Chrome, the two browsers I use most often. I then restarted both programs with an empty cookie folder.
As the EFF post indicates, you can pick up a Facebook cookie by opening one of the sites the service partners with. Using Ghostery, I was able to block Facebook Connect and other Facebook cookies.
After you install Ghostery, click the ghost icon in the top-right corner and choose Options (the Options icon in Chrome). Scroll to Blocking Options, check "Enable bug blocking (experimental)," and check the tracking sites you wish to block.
The Ghostery icon shows the number of trackers on the current page--if no number is shown, no trackers were detected. Click the icon to display the trackers and links to more information. In Firefox, they're listed on a fly-out menu. In Chrome, the information is presented in a scrollable list.
Ghostery's options let you relocate the "alert bubble" that appears when the page opens. The bubble lists the trackers the program has detected and then fades away after a few seconds.
You can manually enter the sites you don't want to prevent from tracking. The last Ghostery option lets you set the add-on's "bug" list to auto-update.
The GhostRank sharing feature is disabled by default. Enable it to send anonymous information to Ghostery's developer about the bugs you encounter as you browse. The information becomes part of the developer's "census of Web bugs across the Internet."
Knowing who's keeping tabs on your Web activities is the first step toward managing the personal information you share with Web services. Being able to block the services you distrust isn't a guarantee your personal information won't fall into the wrong hands, but at least Ghostery provides Web users with a modicum of control over their private data.