Method and Apparatus for Correlating Multiple Cookies as Having Originated from the Same Device Using Device Fingerprinting

Abstract

Information that is useful to distinguish between two or more computer devices (a “device fingerprint”) is collected and stored in a database with corresponding state-management tokens such as HTTP cookies. The database is searched for a fingerprint, and if the fingerprint is found, the corresponding stored token is delivered to a computer device for the device's use in making subsequent requests for resources or services.

1 . A method for recognizing repeat visitors to a website among a plurality of visitors to the website, comprising:
 if a visitor to the website fails to present a cookie, issuing a new cookie and collecting device fingerprint information about the visitor's computer;   storing the new cookie and the device fingerprint information in a database;   tracking activities of each tracked visitor of the plurality of visitors by the tracked visitor's cookie; and   computing a number of unique visitors to the website by reducing a count of tracked visitors to the website by a number of cookie-clearing visitors having different cookies but similar device fingerprints.   
     
     
         2 . The method of  claim 1 , further comprising:
 offering advertising impressions on the website to an advertiser at a price computed based on the number of unique visitors to the website.   
     
     
         3 . The method of  claim 1 , further comprising:
 soliciting a discounted advertising rate based on the number of cookie-clearing visitors.   
     
     
         4 . The method of  claim 1  wherein collecting device fingerprint information comprises:
 transmitting an executable program to the visitor's computer; and 
 receiving data collected by the executable program about the visitor's computer. 
 
     
     
         5 . The method of  claim 1  wherein reducing the count of tracked visitors comprises:
 selecting records from the database having different cookies and similar device fingerprints; and 
 reducing the count of tracked visitors by a count of the selected records having distinct device fingerprints. 
 
     
     
         6 . The method of  claim 1 , further comprising:
 analyzing the database to estimate a time at which each cookie-clearing visitor lost its cookie; and   computing an average lifetime of a cookie based on the estimated times.   
     
     
         7 . The method of  claim 1 , further comprising:
 identifying unique visitors who experienced at least one cookie-clearing event; and   filtering the tracked activities of the tracked visitors to remove tracked activities of unique visitors who were not identified as having experienced at least one cookie-clearing event.   
     
     
         8 . A method comprising:
 transmitting an executable program to a web browser at a client computer, the executable program to cause the web browser to collect information about the client computer;   receiving identifying information about the client computer that was collected by the executable program;   correlating the identifying information about the client computer with previously-collected identifying information about a plurality of computers; and   associating a first browser activity sequence linked with a first persistent activity token with a second browser activity sequence linked with a second, different persistent activity token.   
     
     
         9 . The method of  claim 8 , further comprising:
 before the transmitting operation, receiving a request from the web browser at the client computer to retrieve a resource, the request lacking a persistent activity token; and   after the receiving operation, transmitting a message to cause the web browser to associate the second, different persistent activity token with a subsequent request from the web browser.   
     
     
         10 . The method of  claim 8  wherein the executable program comprises at least one of a JavaScript program, a Java program or a Flash program. 
     
     
         11 . The method of  claim 8  wherein the identifying information comprises at least one of an operating system version, a browser software version, a browser plugin list, or a font list. 
     
     
         12 . The method of  claim 8  wherein the associating operation produces a plurality of tentative associations, the method further comprising:
 collecting distinguishing information about a plurality of browser activities associated with the second, different persistent activity token; 
 comparing the distinguishing information with the first browser activity sequence; and 
 selecting one of the plurality of tentative associations based on similarity between the distinguishing information and the first browser activity sequence. 
 
     
     
         13 . A system comprising:
 a web server to receive requests from clients and deliver requested digital content to the clients;   a database to record information about the requests and the clients; and   client correlation means to collect distinguishing information from the clients and assign unique identifiers to the clients.   
     
     
         14 . The system of  claim 13  wherein the client correlation means is to cause a client to collect and transmit information about the client to the web server. 
     
     
         15 . The system of  claim 13  wherein the client correlation means is to transmit an executable program to the client, said executable program to cause the client to report one of an operating system of the client, a browser software version of the client, a list of browser plugins of the client or a list of display fonts of the client. 
     
     
         16 . The system of  claim 13 , further comprising:
 an analysis server to report a synthetic history of client activities, wherein the synthetic history of at least one client is constructed by combining a first history of requests associated with a first unique identifier and a second history of requests associated with a second, different unique identifier.   
     
     
         17 . A computer-readable medium containing instructions to cause a programmable processor to perform operations comprising:
 receiving a device fingerprint from a client computer;   locating a similar device fingerprint in a database;   extracting a persistent token corresponding to the similar device fingerprint in the database; and   transmitting a message to cause the client computer to adopt the persistent token for a future sequence of requests for digital resources.   
     
     
         18 . The computer-readable medium of  claim 17  wherein the device fingerprint comprises information about the client computer. 
     
     
         19 . The computer-readable medium of  claim 17  wherein the device fingerprint comprises information about an Internet Protocol (“IP”) address of the client computer. 
     
     
         20 . The computer-readable medium of  claim 17  wherein the device fingerprint comprises an approximate geographic location of the client computer. 
     
     
         21 . The computer-readable medium of  claim 17  containing additional instructions to cause the programmable processor to perform operations comprising:
 receiving a request from the client computer; 
 preparing a response to the client computer based on the request and on historical data in the database keyed to the persistent token; and 
 transmitting the response to the client computer. 
 
     
     
         22 . The computer-readable medium of  claim 17  containing additional instructions to cause the programmable processor to perform operations comprising:
 comparing a pair of device fingerprints to estimate a likelihood that the device fingerprints were received from the same client computer. 
 
     
     
         23 . The computer-readable medium of  claim 17  containing additional instructions to cause the programmable processor to perform operations comprising:
 searching the database of device fingerprints to locate a device fingerprint that is most similar to the device fingerprint received from the client computer.