What is an Evercookie?


An Evercookie is a persistent cookie that is hard to remove from your computer because it is designed to be an ever-present-cookie.

The Evercookie

Your bog-standard everyday cookie tends to be a text file that is stored on your computer and that can be deleted by you or removed by your browser.

The ease in which we can delete cookies is not ideal for some and this prompted the creation of cookies that are harder to remove such as Local Shared Object (LSO) cookies, also known as flash cookies. However there are now tools and browser add-ons that can remove these cookies prompting the creation of an even harder to remove cookie: the evercookie.

An evercookie works by making multiple cookies of itself in different formats in the hope that you cannot delete all instances of it before it realises that copies of itself have been deleted and tries to restore them.

In order to remove an evercookie you need to know all the locations and files that it creates on your computer and remove them at the same time. This is not easy as the evercookie is still evolving and tools to remove it are still in development.

Last word

One way of avoiding having to worry about the evercookie is to surf the web from a virtual machine that runs from a bootable iso and does not store any session data.

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Article date: 5th February 2011

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