MT Protect finally gives you the ability to protect entries and blogs within Movable Type in three different ways:
Password protection - protect your entries or blogs with a password which readers must correctly enter to gain access.
Typekey protection - enter the Typekey usernames of readers you wish to grant access and they must login via Typekey to gain access. Typekey users not on the allowed list will not be able to gain access. This type of protection is much safer than password protection as it verifies the identity of your reader.
In the course of using the plugin, you may find that you are allowing access to the same people repeatedly. MT Protect's Protection Groups feature allows you to define sets of any number of people who often garner the same permissions. The protection group -- and hence all of the people in it -- can be granted access to an entry as easily as one person. For all intents and purposes, protection groups are like email aliases in that you only send an email to only one address and yet many can receive it.
You can create as many protection groups as you need to make your use of MT Protect effortless.