Asked for root password on login - seems to be by polkit

I am getting a box coming up when I log into kde on first booting the computer asking for a root password to run sh.
It seems that the request is being generated by polkit.
I don't know what has changed to make this start happening. It is somewhat irritating and I am not keen on entering a root password when I don't reallly understand what it is about. How can I track down the cause of this and stop it?

Thanks