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CAPEC-464: Evercookie

Attack Pattern ID: 464
Abstraction: Standard
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+ Description
An attacker creates a very persistent cookie that stays present even after the user thinks it has been removed. The cookie is stored on the victim's machine in over ten places. When the victim clears the cookie cache via traditional means inside the browser, that operation removes the cookie from certain places but not others. The malicious code then replicates the cookie from all of the places where it was not deleted to all of the possible storage locations once again. So the victim again has the cookie in all of the original storage locations. In other words, failure to delete the cookie in even one location will result in the cookie's resurrection everywhere. The evercookie will also persist across different browsers because certain stores (e.g., Local Shared Objects) are shared between different browsers.
+ Extended Description

The places a persistent cookie is stored on a victim's machine include: 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, caching, Internet Explorer userData storage, HTML5 Session Storage, HTML5 Local Storage, HTML5 Global Storage, HTML5 Database Storage via SQLite, among others.

+ Typical Severity


+ Relationships
Section HelpThis table shows the other attack patterns and high level categories that are related to this attack pattern. These relationships are defined as ChildOf and ParentOf, and give insight to similar items that may exist at higher and lower levels of abstraction. In addition, relationships such as CanFollow, PeerOf, and CanAlsoBe are defined to show similar attack patterns that the user may want to explore.
ChildOfMeta Attack PatternMeta Attack Pattern - A meta level attack pattern in CAPEC is a decidedly abstract characterization of a specific methodology or technique used in an attack. A meta attack pattern is often void of a specific technology or implementation and is meant to provide an understanding of a high level approach. A meta level attack pattern is a generalization of related group of standard level attack patterns. Meta level attack patterns are particularly useful for architecture and design level threat modeling exercises.554Functionality Bypass
Section HelpThis table shows the views that this attack pattern belongs to and top level categories within that view.
+ Prerequisites
The victim's browser is not configured to reject all cookiesThe victim visits a website that serves the attackers' evercookie
+ Resources Required
Evercookie source code
+ Mitigations
Design: Browser's design needs to be changed to limit where cookies can be stored on the client side and provide an option to clear these cookies in all places, as well as another option to stop these cookies from being written in the first place.
Design: Safari browser's private browsing mode is currently effective against evercookies.
+ Taxonomy Mappings
Section HelpCAPEC mappings to ATT&CK techniques leverage an inheritance model to streamline and minimize direct CAPEC/ATT&CK mappings. Inheritance of a mapping is indicated by text stating that the parent CAPEC has relevant ATT&CK mappings. Note that the ATT&CK Enterprise Framework does not use an inheritance model as part of the mapping to CAPEC.
Relevant to the ATT&CK taxonomy mapping
Entry IDEntry Name
1606.001Forge Web Credentials: Web Cookies
+ References
[REF-401] Samy Kamkar. "Evercookie". 2010-09-09. <>.
+ Content History
Submission DateSubmitterOrganization
(Version 2.6)
CAPEC Content TeamThe MITRE Corporation
Modification DateModifierOrganization
(Version 2.8)
CAPEC Content TeamThe MITRE Corporation
Updated Description Summary, Related_Attack_Patterns
(Version 3.4)
CAPEC Content TeamThe MITRE Corporation
Updated Mitigations
(Version 3.7)
CAPEC Content TeamThe MITRE Corporation
Updated Description, Extended_Description
(Version 3.8)
CAPEC Content TeamThe MITRE Corporation
Updated Taxonomy_Mappings
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Page Last Updated or Reviewed: July 31, 2018