Domain reputation is a security score or judgment about whether a domain appears trustworthy. Security systems build it from signals such as registration age, observed abuse, malware hosting, phishing reports, email behavior, DNS patterns, TLS identity, and network location. A “good” reputation can help traffic pass, while a poor score can trigger blocking, challenge pages, sandboxing, or additional review.
It matters because many defenses use domain reputation as a fast filter for web browsing, email, and API access. In attacks, adversaries try to borrow trust by using familiar-looking domains, compromised domains, or shared infrastructure that already has a clean reputation. In shared CDN environments, that can be risky: the visible domain may look safe even when the delivery path or tenant context is different. Strong defenses treat reputation as one signal, then correlate it with certificate details, SNI, Host headers, DNS results, and other routing metadata before allowing access.