Hi
Row level security is usually done to secure data from users on accessing what rows/columns of data can be used. They are primarily used when dealing with large number of users accessing same data but with different functionality levels, say from top management to employee.
"Manage Access Restriction" Option in Universe Designer.In Designer,Go to Tools-->Manage Security-->Manage Access Restrictions--> Specify the Name to Restriction-->In Row tab(Select table and give the condition)-->Assign this restriction to the user/group.(This restricts a user to access values corresponding to the specified condition.
Below tutorial will give you an overview on security profile..
http://scn.sap.com/docs/DOC-22107
Link’s
http://help.sap.com/businessobject/product_guides/boexir4/en/xi4sp5_info_design_tool_en.pdf