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Have you heard of client fingerprinting? As privacy and security become increasingly important, it is crucial to understand the different techniques used to identify and track users on the Internet. This is exactly where such technology comes into play.
What is client fingerprinting?
Client fingerprinting is also known as browser fingerprinting, device fingerprinting, or machine fingerprinting. The technology makes it possible to uniquely identify a web browser or device by capturing specific configuration details and settings. Much like a human fingerprint is unique, this process creates a digital fingerprint that can be used to identify a client across different websites and sessions, and even when using incognito mode.
Essentially, client fingerprinting assigns each client a unique identifier (device ID) based on the specific characteristics of the device. The analogy to the human fingerprint underlines the goal of achieving a high degree of individuality and persistence of digital identification. The ability to distinguish clients even when they are hidden behind a NAT (Network Address Translation) address indicates a highly developed methodology that goes beyond simple IP address tracking.
Although the terms client, browser, and device fingerprinting are often used interchangeably, there are subtle differences in the scope of application. Client fingerprinting is a generic term for methods used to identify the accessing unit. Browser fingerprinting focuses specifically on the characteristics of the web browser, while device fingerprinting encompasses the hardware and software attributes of the entire device and is often used in mobile applications.
How does client fingerprinting work?
The process of client fingerprinting begins when a client connects to an application for the first time. Important identifying information is exchanged between the client and the server or load balancer. This information is stored and remembered for later identification. Often a device fingerprint tracker, typically a JavaScript script, is used to collect detailed configuration data from the client.
These collected data points are combined and often converted into a unique identifier using a hash algorithm. The resulting fingerprint is stored in a database on the server side. On subsequent visits, this process is repeated and the newly generated fingerprint is compared with those stored in the database to recognize the client.
Fingerprinting techniques
- Passive fingerprinting:
Observation of network traffic without direct interaction.
Analysis of HTTP data at the gateway or router. - Active fingerprinting:
Active communication with the target system.
Sending of requests, evaluation of responses.
Active techniques: Network analysis, packet recording, deep packet inspection. - Hybrid fingerprinting:
Combination of passive and active techniques that combine the strengths of both technologies.
Technologies used
- Browser and device information:
JavaScript for data collection. - Specific fingerprinting methods:
Canvas fingerprinting via the HTML5 canvas element.
WebGL fingerprinting via WebGL API.
Audio fingerprinting with the AudioContext API.
HTTP headers and TLS/SSL and TCP/IP protocols are also used to capture information. Older technologies such as Flash and Silverlight were used in the past, but are now obsolete. In the mobile sector, device-specific APIs are often used.
What data is collected for client fingerprinting?
An extensive range of data points is collected for client fingerprinting:
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Who uses client fingerprinting?
Client fingerprinting is used in a variety of industries. Advertisers, for example, use this technology to create user profiles and optimize personalized advertising campaigns. Online retailers use client fingerprinting to analyze customer behavior, create personalized shopping experiences, and detect fraud.
Financial institutions use the technology to prevent fraud by identifying unusual activity to improve the security of online transactions. Law enforcement agencies also use client fingerprinting to monitor and track online activity during ongoing investigations.
Why is client fingerprinting used?
The use of client fingerprinting has several objectives:
- Security: Identifying malicious clients and preventing attacks such as session hijacking, web scraping, and brute force attempts.
- Fraud detection: Detecting fraudulent activity, preventing credit card fraud and identifying multiple accounts from the same device.
- Personalized marketing: Tracking users for targeted advertising and content customization.
- Web analytics: Identifying unique and returning visitors for tracking and analysis. Supporting website optimization by understanding user behavior.
- Bot detection: Distinguishing between human users and bots.
- User authentication: Supplementing traditional authentication methods with device identification.
- Digital rights management (DRM): Preventing unauthorized use of content.
- Rate limiting and traffic management: Controlling access to resources and preventing overloads.
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What are the advantages of client fingerprinting?
This method has numerous advantages. The high level of accuracy is particularly noteworthy, as the combination of various device and browser features enables precise identification. Client fingerprinting is also durable: unlike cookies, which can be deleted or blocked, the digital fingerprint of a device remains stable over a longer period of time.
Another plus point is the independence from cookies, which is particularly advantageous in times of increasing data protection requirements and cookie restrictions. As it is difficult for users to manipulate or conceal their digital fingerprints, fingerprinting offers a robust means of identification.
What are the disadvantages and risks of client fingerprinting?
Despite these advantages, there are also significant risks and disadvantages. Privacy concerns are paramount, as fingerprinting is often done without the explicit consent of users and detailed information about their devices and online behavior is collected. This leads to a lack of transparency, as many users are not aware that their data is being collected and processed.
Fingerprinting is technically in a legal gray area, as there are different regulations in different jurisdictions, which creates uncertainty for companies. There are also technical challenges: While fingerprinting is difficult to circumvent, savvy users can use special tools or system changes to cover their digital tracks.
What is the legal framework for client fingerprinting?
The legal framework for client fingerprinting is complex and constantly evolving, especially with regard to data protection regulations. In the European Union, the General Data Protection Regulation (GDPR) is the central law that governs the processing of personal data. This means that in many cases, companies must obtain explicit consent from users before using fingerprinting techniques for purposes such as advertising or analysis. The ePrivacy Directive (and the planned ePrivacy Regulation) also plays an important role in the regulation of tracking technologies such as fingerprinting.
In the United States, there is no comprehensive federal law on data protection. In California, for example, the California Consumer Privacy Act (CCPA) regulates the handling of personal data, while laws such as the Biometric Information Privacy Act (BIPA) in Illinois set stricter requirements for consent and the protection of biometric data.
Conclusion
Client fingerprinting is a sophisticated technique for identifying web browsers and devices. Despite its advantages, the use of client fingerprinting poses significant concerns and challenges in terms of data protection regulations. Organizations need to take a responsible and transparent approach that leverages the benefits of client fingerprinting without violating users’ rights and expectations.
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