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Home >  Technology > Privacy & Security > Supercookies: The Web’s Latest Tracking Device

Published 18th September 2011 by

Did you delete your cookies? Think again as new research has discovered that major websites such as MSN.com have been using a new kind of supercookie to track your online activities.
Internet Security 101 Series
  1. Introduction to Hacking
  2. History of Cryptography
  3. Online Privacy And Why It Matters
  4. Supercookies: The Web's Latest Tracking Device
  5. Ultimate Guide to SSL for the Newbie
  6. How Internet Security and SSL Works to Secure the Internet
  7. Man in the Middle Hacking and Transport Layer Protection
  8. Social Engineering
  9. Cookie Security and Session Hijacking
  10. What is Cross Site Scripting? (XSS)
  11. What is Internal Implementation Disclosure?
  12. Parameter Tampering and How to Protect Against It
  13. What are SQL Injection Attacks?
  14. Protection Against Cross Site Attacks

What is a cookie

A cookie is a small text file that is stored on your hard drive and is used by sites to tailor your viewing experience. They typically contain information such as last time you visited the side, a session id or any preferences you have set about how you customise the website (font size, colour scheme and so on). These cookies can only be accessed by that one website, and they are entirely optional.

Over the years these cookies have been manipulated into providing tracking information and for providing targeted advertising, and alongside this our browsing habits have changed. We now access the Internet via multiple devices (desktops, laptops, tablets and smartphones to name a few). The traditional cookie cannot be used to track across multiple devices, thus the person doing the tracking can only track what you do on each device, not across all devices. With the recent advent of the "Do Not Track" movement, and some browsers disabling cookies by default or via extensions, the age of cookies is quickly drawing to a close.

Super Cookies

Researchers from Stanford University and University of California at Berkeley have discovered new "supercookies" lurking on some major website which has the ability to identify and track users across multiple devices and multiple websites, with some even being able to access your internet browsing history. These cookies are not controlled by the browser, are difficult to block or identify by users and there seem to be no controls as to what information they capture and what they do with that information.

The exact details of their implementations have not been released, but it has been rumoured that these supercookies will probably gain access to the unique identifiers or serial numbers of your devices and link them to some kind of global account, such as your Microsoft or Google account. Once the unique ID of your smartphone, laptop, TV, and game console has been linked to a central point, it becomes very easy to track your behaviour. Microsoft, Google, Apple or Facebook will know what time of day you wake up from the first time you check email or browse the web, the route you take to work and where you work (via GPS), what job you do via searches, as well as pretty much anything else you do online. Even if supercookies are not to be linked to your Microsoft, Google or Facebook accounts, if it is technically possible, it could allow for skilled hackers to gain access and swipe your information.

Supercookies are stored in different places than regular cookies, such as within the Web browser's cache of previously visited websites, which is where the Microsoft ones were located. Privacy-conscious users who know how to find and delete regular cookies might have trouble locating supercookies. Supercookies have also been found in Microsoft's advertising network, which places ads for other companies across the Internet. As a result, people could have had the supercookie installed on their machines without visiting Microsoft websites directly. Even if they deleted regular cookies, information about their Web-browsing could have been retained by Microsoft.

There is another word for software that installs itself onto a computer without permission, is difficult to get rid of, replicates to many locations, and restores deleted versions. That word is computer virus, and I treat supercookies with the same contempt.

Why do these companies want to know the sites you visit?

Gathering information about your browsing history can offer valuable clues about your interests, concerns or household finances. For example, if you were to start researching a disease online, they can identify you with having, or know someone with the disease, then target advertisements towards prevention or cures at you wherever you go. The data collected about you may be stored remotely without you knowing about it, or where the data is and will more than likely be sold to the highest bidder for large sums of money. And let's not forget that most of these companies also have our credit card, contact, and address details, too.

Let's say you are on Amazon browsing for a few products. You then look at the same products on eBay or another retail site. Both sites feature advertisements served by the same provider (9/10 times DoubleClick network). Then, while reading on a forum site, or looking at the news, you start to see adverts for those same products. How did these adverts get there?

This is called targeted advertising. These ad networks are using third party cookies - cookies set by sites other than the ones you are looking at. The more sites you look at, the more complete the browsing habits and interests that are collected about you. When they serve adverts they know what sites you've been on, what you've looked at, the products you like.

A Real Example

I keep my work and personal data separate. I have a work laptop and a personal laptop. They are entirely separate, I don't do personal stuff, surf personal sites or sign into any personal accounts on my work laptop. Likewise, I don't do anything work related on my personal laptop. There are no ways to connect the two.

That is until I needed to urgent access my personal Gmail on my work computer. Having entered my username, password and authentication code I opened the email and printed the part I needed to. I then signed out and closed the browser. Imagine my surprise when I turned on my personal laptop and was browsing one of the car forums and saw adverts for the products we use at work showing. Just by signing into my Google account, they have linked my work browsing habits to my personal account.

Supercookies in the Wild

So far supercookies have been found to infect the following storage areas on computers:

  • Standard HTTP Cookies
  • Local Shared Objects (Flash Cookies)
  • Silverlight Isolated Storage
  • Storing cookies in RGB values of auto-generated, force-cached PNGs using HTML5 Canvas tag to read pixels (cookies) back out
  • Storing cookies in Web History
  • Storing cookies in HTTP ETags
  • Storing cookies in Web cache
  • window.name caching
  • Internet Explorer userData storage
  • HTML5 Session Storage
  • HTML5 Local Storage
  • HTML5 Global Storage
  • HTML5 Database Storage via SQLite
  • Probably more yet to be found...

One particular pest is called evercookie which seems to be a method for tracking people, has been around since the start, and there is even a WordPress plugin for it. In their own words:

evercookie is a javascript API available that produces extremely persistent cookies in a browser. Its goal is to identify a client even after they've removed standard cookies, Flash cookies (Local Shared Objects or LSOs), and others. evercookie accomplishes this by storing the cookie data in several types of storage mechanisms that are available on the local browser. Additionally, if evercookie has found the user has removed any of the types of cookies in question, it recreates them using each mechanism available.

How to Block evercookie and supercookies

Currently, there is no practical way to block supercookies. Using Incognito or Safe Browsing modes will help, but there is no guarantee that they will block supercookies.

The only sure fire method is to disable JavaScript and block the regular cookies as well, but as I found out most websites simply will not function anymore.

Simply disabling JavaScript will not remove already existing supercookies, but they will be inactive due to the disabled JavaScript support.

Another option, although hardly feasible, is to use a virtual machine. When you're finished browsing the web, simply delete the virtual machine and clone a copy from the master. Next time you start from a clean copy and when you're done, delete it again.

My current techniques for blocking supercookies consist of using the FlashBlock plugin which disables all flash unless I specifically allow an applet to run.

I also use AdBlockPro which most ads and tracking, which speeds up browsing and also blocks cookies by advertisers.

I have also disabled JavaScript, only allowing specific sites to run, same for cookies.

Unfortunately, applications such as CCleaner are unable to remove all records of evercookie so I cannot recommend their use at this time.

What can be done about Supercookies

Simply clearing out your internet history, temporary files and cookies just aren't going to cut it in today's information age, nor are cookie blockers and history erasers.

Do Not Track (DNT) is a technology and policy proposed in 2009 that enables you to opt out of tracking, however, it is not widely implemented and only voluntary.

Unfortunately, the supercookie technology is at the moment in its infancy and a proper defence has yet to be established. For the time being, this is what I do -

  • Use Google Chrome
  • Set cookies to delete when I close my browser
  • Block all third-party cookies
  • Set temporary files to be deleted when I close my browser
  • Install AdBlockPlus addon I can no longer in good good conscience recommend AdBlockPlus as the developers now provide a means for ad publishers to bypass ad blocking through means of an "acceptable ads" policy.
  • Install uBlock Origin
  • Install HTTPS Everywhere
  • Install FlashBlock
  • Do not use web service to resolve navigation errors
  • Do not log into Google account unless I have to
  • Make sure that "Automatically send usage statistics and crash reports to Google" is UNTICKED.
  • Running Windows 10? Geez, you'd better read this: Windows 10 Privacy Settings

Further Reading

  1. Tracking the Trackers: Microsoft Advertising
  2. How to optimise Google Chrome for Privacy
  3. Do Not Track
Tutorial Series

This post is part of the series Internet Security 101. Use the links below to advance to the next tutorial in the couse, or go back and see the previous in the tutorial series.

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