Easily restrict access to your Magento Administration backend just by adding a comma delimited list of IP addresses in System->Configration->Sweet-Apple->Admin IP Address Restriction.
The restriction can be toggled on and off at will.
Please note:
Use this extension with care if you do not have a static address on your internet connection.
This extension overrides Mage_Admin_Model_Observer::actionPreDispatchAdmin method and hence should only be used with Magento 1.7.0, 1.7.1 and 1.7.2. It's easy to adapt for earlier versions should you wish by editing the corresponding Mage_Admin_Model_Observer for your installed Magento version.
If you lock yourself out of the admin area by failing to add your own IP address, there are instructions and a reset script available here (or just delete the key 'sweetapple_admin_ip_lockdown/iplockdown/status' from the 'core_config_data' table.
Still having trouble? Email info@sweet-apple.co.uk for paid support.