You can resolve this issue by using Section Access, see attached document.
The attached version is a simple version and checks for the NTNAME Windows NT Domain user (user login) to see if the user can access the report.
The data is then reduced by the DR_COUNTRY (country) field.
Open the attached and change my NTNAME to yours. Save the document and then make a backup. Once the backup has been created go to Settings > Document Properties > Opening > Select "Initial Data Reduction Based on Section Access".
Reload the document and save and close. Reopen the document and you will see the data has been reduced to the countries you have specified.
A word of warning all the data in Section Access has to be UPPER case!
Thank you for the reply, but I think OSuser will give me the user who is logged in to the server (which most probably is a system user ID). That's not what I need.
I need the credentials of the user accessing/browsing the report. And this user was authenticated through ActivIdentity.
You see, we have a table where all the user authorizations are stored. So, I need to get the credential of the user accessing/browsing the report so I can get his authorization from our authorization table and display the data based on those authorizations.