System Settings : Manage Security Settings : Configure User Lockout Settings
  
Configure User Lockout Settings
User Lockout Settings define how many incorrect log in attempts are allowed by a user before he/she is locked out and the password must be reset.
When a password is being reset by the user through the (Forget Password?) hyperlink, he/she must answer the security question that was set up upon account creation. User Lockout Settings also dictate how many attempts to answer the security question may be answered incorrectly before it must also be reset. You may also specify a lockout period of time and a time interval for locking out a user if desired or needed.
 
*To specify lockout settings:
1. Navigate to Admin > System Settings > Security.
2. Enter the number of times a user may enter the incorrect password or security question before being locked out in the Invalid login attempts allowed field.
The default is five. Any number between 1 and 100 may be entered. If this field is set to 0, the user will never be locked out.
3. Select Locked users can reset their password if users may reset their own passwords from the log in page (through the Forgot Password? hyperlink). Otherwise, an admin will need to reset the password.
4. Set the specified period of time that users are locked out if the password is entered incorrectly (using the invalid login attempts field value) in the Lockout period (minutes) field. In the image above, if the password is entered incorrectly 3 times, the user is locked out for 10 minutes before he/she will be able to try again. The default value is 0 which means there is no "waiting period".
5. If you want the user locked out after the password is entered incorrectly (using the invalid login attempts field value) for a specified time interval, use the Invalid attempt period (minutes) field. In the image above, the user is locked out when the password is entered incorrectly three times within 15 minutes.
 
Tip: You may reset a user’s password by editing the user account.
 
*See Also:
Reset a User’s Password
Unlock a User’s Account
Reset a User’s Security Question
Reset Your Rev User Account Password or Security Question