Internet domains are human-readable names, such as example.com, that map to technical internet resources through the Domain Name System (DNS). They hide IP addresses behind easier-to-remember labels, making websites, APIs, email systems, and other services simpler to find and use. A domain can point to a web server, a content delivery network, a mail provider, or other infrastructure, and it can be changed without changing the name itself.
In cyber security, domains matter because they are both a trust signal and a control point. Attackers register lookalike domains for phishing, malware delivery, command-and-control, or fake login pages. They may rotate domains to avoid blocking or takedown. Defenders monitor domain registrations, DNS records, and certificate activity to spot suspicious infrastructure, block malicious names, and seize or sinkhole domains when legal and operational conditions allow. Because many abuse campaigns rely on ordinary web naming, domains are often the first visible part of an attack.