TCP wrappers therefore control who is allowed to connect to the inetd. This is a good first step from which almost all remote services will be unreachable. This allows one to instead of battling with fixing everything at once, it allows one to concentrate on what services the computer should provide After everyone is denied, controlling what services are offered is the next step on the way to a secure machine. A default linux installation has many services enabled, each a potential entrance for an exploit. Several services are intended only as testing measures and should be commented out as soon as functionality is desired.
Time is simply to give the time of day on the machine.
Ftp is the Washington University ftpd that is default on most linux installations. Comment this out until one is prepared to check this against current versions of wu.ftpd. Some services in which I insist upon commenting out include pop3, rlogin, rsh, finger, talk, exec, ntalk, netstat, and systat. If it is a service that the machine should offer, the admin should do some investigation into the most current version of the program, and the reasons for the upgrade. Netbios and sun-rpc services also fall into this category.