What are the guidelines for changing a password?

A password must comply with the following requirements:

• Eight characters long
• Contain three of the four character groups:
  • At least one uppercase character (A-Z)
  • At least one lowercase character (a-z)
  • At least one numeric character (0-9)
  • At least one special character, consisting of the following: ! " # $ % ' ( ) * + , - . / : ; = ? @ [ \ ] _ ` { | } ~
• Passwords can only be changed once every 48 hours