When a user detaches a database from MS SQL Server, it sets the owner of the data and log files to that user. It also removes all non-owner permissions from the files. This is partially explained at http://msdn.microsoft.com/en-us/library/ms189128.aspx
I have tested this on the following versions of SQL Server
- 2008 R2
Is it possible to change this behavior so file permissions are retained when a database is detached?