You can enable case-sensitive keyword filtering for all your filter lists. Keyword filtering is disabled by default (that is, filtering is not case-sensitive).
To globally enable case-sensitive keyword filtering-
In the Forefront Protection 2010 for SharePoint Administrator Console, click Policy Management, and then, under the Filters section, click Filter Options.
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In the Filters - Filter Options pane, in the General Settings section, select the Enable case-sensitive keyword filtering check box, and then click Save.