{
  "patent_number": "US 6195698",
  "country": "US",
  "title": "How Websites Use Distorted Text Riddles to Stop Bots",
  "original_title": "Method for selectively restricting access to computer systems",
  "summary": "This patent describes the original method for creating CAPTCHAs, using distorted text or audio riddles to distinguish human users from automated bots.",
  "what_it_does": "The patent outlines a security process where a server challenges a user to solve a simple puzzle before granting access to a system. When a client requests access, the server generates random characters and modifies them—for example, by changing fonts, rotating letters, or adding background noise—to create a riddle that is easy for a human to read but difficult for a computer program to interpret. The server then checks if the user's answer matches the original string within a set time limit. If the answer is correct, the connection is allowed; if not, or if time runs out, the server assumes the requester is a bot and terminates the connection.",
  "what_it_does_not_cover": [
    "Does not cover non-riddle based bot detection, such as behavioral mouse tracking or IP reputation analysis.",
    "Does not cover biometric authentication methods like fingerprint or facial recognition.",
    "Does not cover systems that rely on pre-existing user accounts or passwords for verification.",
    "Does not cover challenges that require solving logic puzzles or identifying objects in photos (like modern image-based reCAPTCHA)."
  ],
  "filed": "1998-04-13",
  "granted": "2001-02-27",
  "expires": null,
  "status": "active",
  "holder": "Compaq Computer Corp",
  "holder_url": "https://patentbrief.org/company/compaq-computer-corp",
  "inventors": [
    {
      "name": "Andrei Z. Broder",
      "url": "https://patentbrief.org/inventor/andrei-z-broder"
    },
    {
      "name": "Krishna Bharat",
      "url": "https://patentbrief.org/inventor/krishna-bharat"
    },
    {
      "name": "Mark D. Lillibridge",
      "url": "https://patentbrief.org/inventor/mark-d-lillibridge"
    },
    {
      "name": "Martin Abadi",
      "url": "https://patentbrief.org/inventor/martin-abadi"
    }
  ],
  "times_cited": 219,
  "tags": [
    "consumer_electronics",
    "software",
    "telecommunications",
    "ai_ml"
  ],
  "abstract": "A computerized method selectively accepts access requests from a client computer connected to a server computer by a network. The server computer receives an access request from the client computer. In response, the server computer generates a predetermined number of random characters. The random characters are used to form a string in the server computer. The string is randomly modified either visually or audibly to form a riddle. The original string becomes the correct answer to the riddle. The server computer renders the riddle on an output device of the client computer. In response, the client computer sends an answer to the server. Hopefully, the answer is a user's guess for the correct answer. The server determines if the guess is the correct answer, and if so, the access request is accepted. If the correct answer is not received within a predetermined amount of time, the connection between the client and server computer is terminated by the server on the assumption that an automated agent is operating in the client on behalf of the user.",
  "url": "https://patentbrief.org/patent/us/6195698/google-search-engine",
  "markdown_url": "https://patentbrief.org/patent/us/6195698/google-search-engine/md",
  "google_patents_url": "https://patents.google.com/patent/US6195698",
  "relatedPatents": []
}