By default, the account sharing functionality is enabled when MemberMouse is installed. It can be disabled by going to MM > General Settings > Other Settings.

MemberMouse will inspect login events over a 24-hour period for each account. If, during a 24-hour period, an account is logged-into from over 5 different IP addresses, then MemberMouse will automatically lock that account. The Member Status Lifecycle article explains more about the "locked" account status.

You can make the account sharing protection more or less strict by changing the number of IP addresses allowed. Increasing the number makes it less strict, while decreasing the number makes it more strict.

When an account is locked, this will have no effect on the billing aspects of the account. You can unlock an account from the Access Rights tab of a member's account.

You can review login activity in a member's activity log, including the IP addresses from which they logged in, in order to determine why the account was locked. This article demonstrates how to use the activity log: Auditing Member Activity Using the Activity Log.