The login object is really composed of two parts: the login object itself
(/adm/obj/login.c) and a banish daemon (/adm/daemon/banish.c).  The
banish daemon keeps track of things like sites which need to register
in order to get into the Mud, names to be watched, etc.  You can
restrict access in these manners:

Making sites register characters:
Using the command register, unregister, and whoregistered, you can set
sites which must first register a character before being allowed
to play the mud.  Once a player from a site on registration sends
you email and registers, you can use the commands allow, unallow, and
whoallowed to deal with those exceptions from the registered sites.
Once a character allowed in logs in, the name is removed from the allowed
list.  Players with characters are exempt from the registration block on
login.

Banishing names:
You will want to make it so characters cannot use certain names.  Offensive
words, names of active monsters, etc are things you want to banish.  Use
the banish, unbanish, and whobanished commands to deal with this.

Watching sites and players:
You can keep an eye on certain players or sites using the watch, unwatch,
and whowatched commands.  Whenever a watched player, or a player from a 
watched site logs in, it logs that login to a special file in the /log/watch
directory.

Guests:
When the mud is locked, you can allow in people not meeting the normal
criteria for being allowed on the mud using hte addguest, removeguest,
and whoguests commands.  Normally, only members of certain groups are
allowed on the mud when it is locked.  This is useful for player testing
and development.

Preventing unwated substrings in names:
You can prevent people from logging in with certain substrings in their
names.  For instance, you do not likely want anyone to have any name
formed witht he word "fuck".  Using the stopstring, unstopstring,
and stopstrings commands you can administer this functionality.

The config.h include file allows you to define certain characteristics
for character making and such.  There is a define which determines if the
mud is locked or open to everyone.  You can define the maximum number of
letters and minimum number of letters allowed in player names.  You
can define which mud groups are allowed in when the mud is locked,
and you can define how much time a player has to log in before the login
times out.  Finally, you can define the number of wrong password
entries allowed before the login is disconnected.