Multiple login attempts from different IP Addresses
You can use Rename Admin Paths module to override the admin path.


  This module allows you to:

rename path like '/admin/...' to '/something/...'
rename path like '/user/..' to '/something else/..'

  
  It can be effective against registration spam bots or malicious
  people.


And using the Login Security module you can


  
  limit the number of invalid login attempts before blocking accounts,
  or deny access by IP address, temporarily or permanently.
  
  
  A set of notifications by email or Nagios may help the site
  administrator to know when something is happening with the login form
  of their site:
  
  
  password and account guessing,
  bruteforce login attempts or just unexpected behaviour with the login 
  operation.
  
  
  For alternative controls, Login Security can disable Drupal core's
  login error messages, obfuscating the reason for the login failure.
  This could make it harder for an attacker to discover whether the
  account even exists.


The use of the Flood control module is another option to control variables like the login attempt limiters and any future hidden variables.