LFCS: Linux Foundation Certified System AdministratorDemo

tcpd, the TCP Wrappers daemon, intercepts incoming connection requests to services that are compiled or configured with libwrap support. It consults /etc/hosts.allow (and /etc/hosts.deny) to determine whether the requesting client should be permitted or denied access to the requested service, checking hosts.allow first and applying the first matching rule. This host-based access control mechanism is the core purpose of tcpd, distinguishing it from super-servers like inetd/xinetd (which launch services but don't inherently use hosts.allow) and from individual daemons like fingerd or mountd (which are the services being protected, not the access-control mechanism itself).