Supercookies in the Wild
- Introduction to Hacking
- History of Cryptography
- Why Privacy Matters
- Supercookies in the Wild
- Ultimate Guide to SSL for the Newbie
- How Internet Security and SSL Works
- Man in the Middle Hacking and Transport Layer Protection
- Cookie Security and Session Hijacking
- What is Cross Site Scripting? (XSS)
- What is Internal Implementation Disclosure?
- Parameter Tampering and How to Protect Against It
- What are SQL Injection Attacks?
- Protection Against Cross Site Attacks
Supercookies provide a means by which you can be tracked online regardless of if you clear your browser cache, temporary internet files or even disable traditional cookies.
At the time of writing that previous article, supercookies were in the infancy stages of development and only used by a few websites such as MSN and Google. Now, a year later, they have evolved into commercial products and they are everywhere. Supercookies are also an easy way for advertisers and trackers to evade the "Do Not Track" option of browsers .
Supercookies are now being used to identify and track you via your internet browser even after you remove standard cookies, delete Flash cookies (Local Shared Objects or LSOs), delete Silverlight storage, delete temporary internet files and wipe out anything else. In fact, they are very difficult to get rid of, because if one of the storage locations gets deleted, itself replicates from another location. It is estimated (at the time of writing) the 1.5% of the top 1 million sites use supercookies (that's 15,000 websites and growing) .
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.
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 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.
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.
Unfortunately, applications such as CCleaner are unable to remove all records of evercookie so I cannot recommend their use at this time.