An Internet-protocol blocker is a service or software that prevents IP addresses from accessing a particular service, website or computer on a network. Firewalls are a common IP-blocking tool, and are found on most residential routers.
IP addresses are tied to devices on a network and identify a computer when it connects to other networks. IP blocking is used to prevent unauthorized access to private networks, such as business systems and home computers. It can also be used by Internet-service providers to block spam email from being sent across its network, or to prevent malicious activity. Due to international copyright laws, IP blockers often prevent access to foreign services and media.