The 24-year-old "Harry Potter" alum and U.N. women global goodwill ambassador made headlines last September when she launched the "HeForShe" campaign, which aims to enlist 1 billion men and boys in the movement for gender equality. After Watson delivered her speech, she said a new website popped up threatening to release naked pictures of her.
Watson said she knew the threat was empty, because she'd never taken any nude photos, but that didn't make it any less cruel.
"I knew it was a hoax. I knew the pictures didn't exist," she told an interviewer Sunday during a HeForShe webcast. "But I think a lot of people that were close to me knew gender equality was an issue but they didn't really think it was that urgent or particularly, you know, 'We live in Great Britain. This is a thing of that past.' ... And then when they saw that the minute I stepped up and talked about women's rights, I was immediately threatened -- I mean, in less than 12 hours I was receiving threats -- and I think they were really shocked and, particularly, one of my brothers was very upset."
Watson talked about the cruel prank while answering fans' questions for International Women's Day. The interview was later posted on her Facebook page, which has 30 million fans.
"So I think it was just a wake-up call of, 'Oh, this is like a real thing, it's really happening now. Like now,'" she said. "Women are receiving threats in all sorts of different forms. That was just one specific one."
She added, "If anything, it made me so much more determined. I was just raging. It made me so angry that I was just like ... 'This is why I have to be doing this!' ... So if anything, it actually, if they were trying to put me off it, they did the opposite."
Check out the video below. Watson launches into the story around 5:30 into the video: