Locksmith supports permitting visitors based on their IP address.
Start by opening the settings for a lock you've created. Then, follow the steps shown to add a key that permits "if the customer has a certain IP address", as shown below:
This key can be configured with a series of IP addresses, one given per line. It can also be configured with CIDR definitions, allowing you to specify entire subnet ranges.
This key condition can be inverted, resulting in a condition that permits unless the visitor has a certain IP address. When used with a lock on your entire online store, this is a useful way to block certain visitors.
To accomplish this, invert the key condition, as shown below by clicking on the checkbox next to "invert". (To learn more about inverting conditions, see Inverting keys in Locksmith.)
Because of the way IP address detection works, a IP address key on your entire store will show everyone a spinner graphic for a moment, before your store's content is loaded. This will only happen once, if the visitor has an accepted IP address.