"AccessByIP" is a package for Joomla! 2.5.x and 3.x that consists of an authentication plugin (accessbyip) and an associated login module (mod_accessbyip). The plugin authenticates on the basis of the web browser IP address. The module provides an interface to provide simplified log-ins, in conjunction with the plugin. Released under GNU/GPLv3 licence. A full description and documentation for this package are to be found here.
Please Note this package is limited to one user ID and one block of IP addresses on each web site. AccessByIp-Pro, a more fully-featured extension that is better suited to high-traffic and commercial web sites is now also available.
If you use AccessByIP, please post a rating and a review at the Joomla! Extensions Directory.