Websites including the FBI, Universal Music and Recording Industry Association of America were taken "offline" by the Anonymous group hours after Megaupload was closed down.
Mr Bruce told the Herald he did not know exactly who had helped him - or how - but within a day he had an email with the details of the hacker, believed to be a 35-year-old man living in Madrid with his mother.
He has passed the information on to police in Spain and is waiting for their response.
The website included a store where copies of Mr Bruce's documentaries could be bought, including the award-winning Inside Child Poverty - A Special Report. He donates all sales from that DVD and a percentage from others to a charity that provides breakfasts for hungry schoolchildren.
As a result of the hacking, the website will now be out of action for at least a month and it will cost a significant amount of money to get it working again.
"In bringing down the site he was bringing down a charity, basically," Mr Bruce said.
"I posted on Facebook 'can anybody help me with this' because I don't understand how all this hacking stuff works. It's beyond me.
"Two or three people picked it up and, as I understand, they contacted some top hackers in a group called Anonymous."
Mr Bruce was told that hackers had a code of conduct and Anonymous was upset by what had happened to his site.
"Apparently, one of the rules is you don't hack charity sites, you don't hack sites of people trying to help kids. This guy was trying to impress them, to try and get into their group and boasting about what he'd done - but they turned on him, they chased him."
Mr Bruce said it was good to see Anonymous doing the right thing.
"This is the other side of this group. I'm not going to make comment about what they do in other areas, but this was a real Robin Hood thing. They just decided this was not good. It's extraordinary."
PROVIDING FOOD
* Copies of Inside Child Poverty documentary can still be bought online.
* See: tinyurl.com/cqcwl37
* Proceeds go to children's charities.
