Systems and methods for identifying and characterizing client devices

A system, comprising:

• a first computer that has circuitry forming one or more processors and memory storing instructions to be executed by the one or more processors, the first computer operative upon execution of the instructions to perform an offline configuration process that comprises:
• create an index that associates each of a plurality of tokens with one or more known client devices, and create a lexicon file of tokens used in the index, wherein the index and the lexicon file are established prior to a request for content from a client device;
• wherein the lexicon file identifies one or more high-value tokens and one or more other tokens;
• send the index and the lexicon file to a second computer;
• the second computer having circuitry forming one or more processors and memory storing instructions to be executed by the one or more processors, the second computer operative upon execution of the instructions to:
• (i) receive the request for content from a client device, the request including information about the client device;
• (ii) generate one or more tokens from the information in the request, based on the lexicon file;
• (iii) identify the client device as a particular one of the one or more known client devices, based on a comparison of the one or more tokens generated from the information in the request and the index.