From https://support.google.com/websearch/answer/86640You may see Our systems have detected unusual traffic from your  computer network if Google detects that a computer or phone on your  network may be sending automated traffic to Google.Automated traffic includes:Sending searches from a robot, computer program, automated service, or  search scraper Using software that sends searches to Google to see how  a website or webpage ranks on GoogleWhen this happens in Google Books, what are some possible criterions that Google Books or similar sites can use to  detect that a compute may be sending automated traffic to their sites?
How does Google Books detect unusual traffic from a computer?
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