TCP wrapper is a security tool that allows you to restrict the access to a network service based on the source IP address or hostname of the client. TCP wrapper works by intercepting the incoming connection requests to a service and checking them against a set of rules defined in the /etc/hosts.allow and /etc/hosts.deny files. If the client is allowed, the connection is passed to the service. If the client is denied, the connection is rejected and an error message is logged. Reference:
LPI Linux Essentials: 1.5 Security and File Permissions: 1.5.3 Network Security LPIC-1: System Administrator: 102.5 Implement basic network security: 102.5.1 TCP Wrappers