Marking your media as Unlisted means that your media will not be found in Kaltura MediaSpace either by browsing the site or by searching. But the media will remain accessible so that if you share a link to it with others, they will be able to access it without having to login. But if this link is shared by others or added to another web site, it may become public to the world. It is important to note that marking your media as Unlisted still publishes your media. It just makes it less discoverable. This is a suitable solution for discreet but not sensitive material.
You can mark your media as Unlisted by choosing the Publish option from the Actions menu underneath your media and then choosing the Unlisted option.