To prevent companies from scraping your site, you can implement several measures such as using a `robots.txt` file to indicate which parts of your site shouldn't be accessed by web crawlers, placing content behind a login-wall, using anti-scraping tools or services, and employing obfuscation techniques to make scraping more difficult. Additionally, watermarking your content and issuing legal notices or cease-and-desist orders to offenders can help maintain ownership and deter unauthorized use of your content.