Recently, there was posts on Password Strength - on different programming/testing Facebook community.
Here are some details:
And a Blog post from TechNet:http://blogs.technet.com/b/plitpromicrosoftcom/archive/2009/10/16/si-a-has-a.aspx
(Note: I have translated to English)
Summary for the posts:
Secured password must have:
At least 8 characters
A combination of: uppercase or lower case letters (A-Z or a-z), numbers (0-9) and special characters (?_!@#)
A combination of: uppercase or lower case letters (A-Z or a-z), numbers (0-9) and special characters (which also includes - Alt+Special Chars)
The below table displays: An attacker can hack a password – based on the password rules implemented.