Network Ten has released the first trailer for its upcoming telemovie Underground: The Julian Assange Story, about the early life of the WikiLeaks founder.

Underground has already generated enormous interest overseas and will premiere at the Toronto International Film Festival, which begins tomorrow.

It is a rare honour for an Australian made-for-television film to feature in an international festival.

The telemovie explores Assange's life as a teenage hacker and stars West Australian Academy of Performing Arts graduate Alex Williams in the pivotal role. It also stars Rachel Griffiths and Anthony LaPaglia.