Unauthorized access প্রতিরোধে ব্যবহৃত হয় -

firewall, type of system used to monitor connections between computer networks. One of the earliest responses to malicious activity perpetrated through the Internet, firewalls became a standard part of corporate, governmental, and personal networks.

Typically, a firewall allows no direct connection between the internal network and the Internet. Instead, external connection requests, or digital packets, may be routed to a heavily secured “bastion host” server designed to withstand attack or to a larger “demilitarized zone,” a controlled network between the internal network and the outside. The firewall then evaluates the packet based on programmed security policies and decides whether to permit or deny access. A firewall can regulate access going either to or from the internal network; for instance, some companies use a firewall to block employee access to certain public websites.

source - britannica website