!!Password Policy Filters
When you enable "[Passwords Must Meet Complexity Requirements]" then the password filter is enabled.

[Passfilt.dll] is Microsoft's implementation of a [password filter.|Active Directory and Passwords]

[From Microsoft on Passfilt.dll|http://msdn.microsoft.com/en-us/library/ms722458(v=VS.85).aspx|target='_blank']

Strong password enforcement can be enabled by using the system administration tools. 

The following complexity requirements are enforced by strong password enforcement:
* Passwords may not contain your user name or any part of your full name.
* Passwords must be at least six characters long.
* Passwords must contain elements from three of the four following types of characters.
||Character types||Examples
|English uppercase letters|A, B, C, … Z
|English lowercase letters|a, b, c, … z
|Westernized Arabic numerals|0, 1, 2, … 9
|Non-alphanumeric characters (special characters)|$,!,%,^
|Unicode characters|€, Γ, ƒ, λ
 
!!Windows 2008
Windows 2008 does support multiple password policies in the same domain. 

However, as far as we know, the policy settings are the same basic policies that are in Windows 2000 and Windows 2003. The available settings are often not robust enough for many organizations.

!! More Information
There might be more information for this subject on one of the following:
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