Host Allows - Want to restrict access to certain IPs or certian IP masks? This is the place to put those permissions. psy will disallow access to anyone not listed here. To allow anyone (provided they have the correct username and password) set this to "*".
This is done when you configure psybnc. Here is another way:
/addallow [IP or mask] --- lets whatever IP or mask you specify connect to the bnc. IPs can be definite, ie. 12.12.12.34 or masked, 12.12.12.*. You can also use hostnames and masks such as *.myisp.com.