Supercookies

Supercookies represent sophisticated tracking mechanisms that endure beyond regular cookies. This article outlines what supercookies are, their significance, and their implications for online privacy.

What Are Supercookies?

Supercookies are tracking markers that are stored in ways that go beyond conventional browser cookie storage. Unlike ordinary cookies, they can persist even after cookies have been removed or browsers reset, making them much more enduring.

While traditional cookies depend on storage managed by browsers, supercookies utilize alternative systems such as browser cache, HTML5 storage, ETags, HSTS flags, or even injection at the ISP level. Their difficulty in detection and elimination presents serious issues regarding privacy and transparency.

From a technical standpoint, supercookies cannot be classified as a singular technology. They encompass a range of methods aimed at re-identifying users across various sessions, devices, or networks. Much of the conversation surrounding supercookies intersects with subjects such as browser fingerprinting, tracking scripts, and persistent identifiers.

Main Characteristics of Supercookies

• Exceptional persistence exceeding typical control measures: Supercookies are crafted to endure actions that usually eliminate tracking information. Even if users remove browser cookies, reset configurations, or undergo session changes, supercookies can resurface and still identify the same individual.
• Alternative storage methods: Instead of limiting themselves to a single storage technique, supercookies establish identifiers across various domains, including browser cache, HTML5 localStorage, ETags, HSTS flags, or service workers. This multifaceted storage strategy complicates detection and removal processes.
• Automatic re-identification: When users erase visible tracking information, supercookies can regenerate standard cookies by extracting information from concealed storage. This operation reinstates the original identifier without requiring any action from the user.
• Restricted visibility and control for users: Most browsers do not transparently display the locations of supercookies. Users frequently do not possess integrated features to view or manage these identifiers, which diminishes transparency and the ability to provide informed consent.

Applications of Supercookies

• Long-lasting advertising tracking: Advertisers utilize supercookies to track users over prolonged durations. This method allows the connection of ad impressions to eventual conversions, even after users have removed cookies or switched to different browsers.
• Enhanced detection of fraud and abuse: Financial institutions and online services may leverage persistent identifiers to spot repeat offenders. Supercookies assist in recognizing users attempting to circumvent restrictions via account resets.
• Accuracy in cross-session analytics: Analytics firms depend on techniques resembling supercookies to ensure consistent visitor metrics. This guarantees a more stable collection of user data when standard cookies fail or become outdated.
• Identification at the network level: Some ISPs have implemented supercookies to insert identifiers into HTTP headers. This strategy facilitates tracking at the network level, apart from just through individual websites.
• Profiling user behavior: Supercookies allow for comprehensive behavior analysis across multiple visits and platforms. This capability aids in detailed user segmentation but notably amplifies privacy concerns.