Your exposure setting determines who can zlocate you or receive login and logout notices about you. There are several options for exposure settings that will be explained in detail below. The command to change your exposure is
zctl set exposure net-announced
where net-announced is the setting you have chosen. net-announced may be replaced by any of the exposure settings mentioned in this section. The net-announced setting provides the most information to the largest number of users. Anyone (with or without Kerberos tickets) can find out if you are subscribed to Zephyr, and those people who have you in their .anyone file will receive login and logout notices about you. This means that people using the www zlocate gateway at http://www.mit.edu/zlocate, and those using zephyr at other realms (e.g. ANDREW.CMU.EDU, FSCK.COM) will be able to zlocate you in addition to people who are logged in with valid Kerberos tickets.
The setting realm-announced is like net-announced except that only people with Kerberos tickets in the realm ATHENA.MIT.EDU (which you receive upon login to your Athena account) can check your online status.
net-visible is in practice the same as net-announced. realm-visible is just like realm-announced, except that no login or logout messages are sent.
The opstaff setting means that only Operations Staff are able to access information about you. You are not zlocatable nor are login or logout announcements sent when this setting is used.
Lastly the none setting does not allow information to be given out in the form of login or logout notices or zlocate. It also is the only setting in which you are not able to receive zephyrgrams.