Sorry, your reply got lost in my spam folder.

I am know quite convinced that the fact that I cannot share the internet connection inside the company network (at least via wlan) is of course good for the security of the companies data and that anything I may try is a kind of hack or attack.

There is even a phrase for that:Rogue Access Points
If you succeed to share your internet connection via wifi may be few days later your sysadmin knocks at your door.

That is not my intention. When I am abroad I am using a usb stick and share the connection via Umts between my laptop and the n900. I am using the windows software Virtual Accesspoint for that. That works fine and is a lot of fun. When I have to work in my office it is probably good that I play not too much with the n900.