Restricting the access to the critical Joomla directories such as administrator/ by IP address is a good security measure. This way you can allow access to your Joomla backend only from your own IP address.
In order to implement such a restriction you have to add the following lines in your .htaccess file residing in the directory you wish to protect:
Deny from all
Allow from 220.127.116.11
Note : the sample IP address 18.104.22.168 has to be replaced with your own IP.