GPTBot is OpenAI’s web crawler

OpenAI's web crawler has a user-agent:

User agent token: GPTBot
Full user-agent string: Mozilla/5.0 AppleWebKit/537.36 (KHTML, like Gecko; compatible; GPTBot/1.0; +https://openai.com/gptbot)

Which means it can be restricted to crawl your site using robots.txt:

User-agent: GPTBot
Disallow: /

Found in OpenAI's documentation.