Sometime on Nov 28, Manish Jethani assembled some asciibets to say:
I want to know how I can block telnet access to my machine _when_a_specified_condition_is_true_.
/etc/security/limits.conf
fool around with it a bit. You may also be able to do something with pam, since the telnet service uses pam to determine if login should be spawned or the connection rejected.
Philip