How to use Last name then first name for author name?

I don't always know the first names of authors so I would prefer to sort them based on their last name. 
So instead of:
Cory Doctorow - [Little Brother #1] - Little Brother (2008) [0765319853].pdf
how can I obtain:
Doctorow, Cory - [Little Brother #1] - Little Brother (2008) [0765319853].pdf

Thanks. 