SSAS-Data Security

Hi,
SSAS provides the way to secure analysis services database/cube data from unauthorized access. Analysis services provides secure access by creating object called "roles". After creation of role, user's windows login credential can be used to enroll into particular role because analysis services identifies user from their windows login credentials . You can protect your data in roles at two levels:
1) Dimension level
2) Cell level
If user has been assigned more than one role, analysis services loop through all assigned roles after login. Analysis services finds all permission level for the particular user and union all the permission levels.
If two roles has contradictory access for user then particular access will be allowed. Suppose role1 says Australia data access and role2 denies Australia data access then access to Australia data will be allowed.

http://learnmicrosoftbi.blogspot.com/2010/10/ssas-data-security-dimension-and-cell.html