Hotlink
Direct-link to a resource (often an image) on someone else's server from your own page. <img src="https://other.com/img.jpg">. The host pays the bandwidth — historically shame-worthy practice.
Countermeasure: hotlink protection via Referer header check (nginx, Apache, Cloudflare). When referrer is from another domain → return 403 or a "stop hotlinking" image. CDN (Cloudflare) offers hotlink protection as a click feature. Modern reality: HTTPS + Referrer-Policy makes it harder (can't reliably verify referer). Acceptable hotlinks: CDN links (jsdelivr, cdnjs), embed services (YouTube, CodePen, Twitter — designed to be hotlinked).