The tcp_wrappers package provides a tiny daemon called tcpd that is called by inetd instead of by the actual service daemon. The tcpd program logs the source address of each incoming connection, and can also filter them to allow connections only from trusted systems.

To use tcpd, you can insert it into your inetd as follows:

ftp     stream  tcp     nowait  root    /usr/sbin/tcpd  in.ftpd -l -a
telnet  stream  tcp     nowait  root    /usr/sbin/tcpd  in.telnetd