Cloudflare's **Browser Integrity Check (BIC)** looks for common HTTP headers abused most commonly by spammers and denies access to your page.

It also challenges visitors without a user agent or with a non-standard user agent such as commonly used by abusive bots, crawlers, or visitors.

[BIC is enabled by default](https://developers.cloudflare.com/waf/tools/browser-integrity-check/).
