This module allows you to make usernames for your users case sensitive. What this means is you can have a user with the name 'admin' and 'AdMiN' and they will be treated as seperate users as far as drupal is concerned.
Stock behaviour for Drupal 7 on MySQL is for names to be case insensitive. This can make it easier for attackers to guess usernames
Features
Integrates with MySQL at the moment, and alters the 'name' column in the {users} table to be of type 'varbinary(60)'
Provides a checkbox on the 'admin/config/people/accounts' page where you can switch the case-sensivity on and off
Important points to note with a case-sensitive collation
You will need to tell your users that they must login with their exact username
If you create two users 'Admin' and 'admin' for example, you will not be able to switch back to case in-sensitive usernames without first deleting one of the users