When you specify that a bulk load operation is to be performed as a transaction, you use the TempFilePath property to specify a folder in which to create the temporary files.

The bulk load process creates these temporary files with the following permissions:

• Read/Write/Delete access is granted to the bulk load process.
  
  
• Read permission is granted to all users, because the account under which Microsoft® SQL Server™ is going to access these files is unknown. You can restrict the access to these temporary files by setting the appropriate permissions on the folder that contains them.