Hello,
Currently, I am taking a Computer and Network Security course and have a question om my HW that asks for the six entries on the ENS /etc/hosts.deny file. We need to specifically address what each listed service does and what the system implications are for the entry in the /etc/hosts.deny file. At this time I have researched info on the file but am not finding such info. regarding to the entries. If anyone can direct me in the right direction for this info, I will greatly appreciate it.

Thanks in Advance

The files /etc/hosts.allow and /etc/hosts.deny are used by a library named libwrap.so from the package tcp-wrappers (tcp_wrappers-libs-7.6-52.fc9.i386 in F9) and any "server" linked with it.
Common "servers" are sshd, rsyncd, cupsd, etc.
To check if a given server has support to tcpwrapper, check if it was linked to libwrap (ldd /usr/sbin/sshd | grep libwrap). If it is, than you can control its access using /etc/hosts.allow and /etc/hosts.deny files.
Think hosts.allow and hosts.deny as an access control on the application level, a kind of firewall for specific applications, not protocol/port as usual.

Once we modify host.deny, do we have to restarrt any service to make it effective?