The security settings under the Settings tab are mostly centered around the needs of private or internal knowledge bases. By default, your knowledge base will be visible to the public which means anyone can peruse your content. However, under Settings > Security, you have quite a few options.
When would I use the different types of security?
IP-based Restriction —
This setting is great for internal office knowledge bases. If you can track down the IP addresses that your office uses, you can paste the comma separated list into the box and ensure that no one trying to access your knowledge base from outside of your office can get in.
Shared Password —
This one is great if you need to restrict access to your knowledge base but you aren't sure of your office's IP addresses or if your readers are going to be spread out. Creating a single password that you can give to everyone will allow you to control who gets in but will allow for more flexibility.
IP-based Restriction OR Shared Password—
You can also use this setting in combination with the IP protection setting for even more flexibility. What this means is that while someone is in your office they won't have to worry about logging in because they are accessing the knowledge base from an approved IP address. If they work from home one day though, they will be asked for the shared password to log in.
IP-based Restriction AND Shared Password —
Need more security? You can select to use IP-based restriction as well as a shared password for two-factor authentication.
Approved Readers —
Readers offer the most power in terms of authentication to your knowledge base. Essentially a reader is an individual login for each person or group whom you want to give access to your knowledge base. With this setting turned on, a person trying to access your knowledge base will be asked for a username and a password which we can then use to identify who they are. Once they log in, they will remain authenticated for 2 hours and can browse normally. If you select this option, you will need to set up readers under Your Account > Readers.