East Turkestan: Chinese Hack Film Festival Site
In an earlier protest on Friday, Beijing withdrew four Chinese films.
Melbourne's The Age newspaper says private security guards have been hired to protect Kadeer and other film-goers.
She is due to attend the screening of Ten Conditions of Love, by Australian documentary-maker Jeff Daniels, on 8 August.
Chinese authorities blame Kadeer, leader of the World Uighur Congress, for inciting ethnic unrest in Xinjiang - charges she denies.
Earlier this month, around 200 people died and 1,600 were injured during fighting in the region between the mostly Muslim Uighurs and settlers from China's Han majority.
Kadeer, 62, spent six years in a Chinese prison before she was released into exile in the US in 2005. In 2004, she won the Rafto Prize for human rights.
Richard Moore, head of the Melbourne International Film Festival, told the BBC that he had come under pressure from Chinese officials to withdraw the film about Kadeer and cancel her invitation to the festival.
He said the attacks on the festival's website began about 10 days ago.
"We've been subjected to a number of these attacks and we can see behind the scenes on our website that there are hundreds, well, if not thousands, of people from outside of Australia trying to get into our website and trying to damage us," Mr Moore told the BBC's World Today programme.
"This has been going on... since obviously the call from a Chinese consular official who told me in no uncertain terms that I was urged to withdraw this particular documentary from the film festival and that I had to justify my actions in including the film in our programme," he went on.
"Hey, we're an independent arts organisation and it's our programme!"
He said police were investigating the website attacks, which appear to come from a Chinese internet address.