The Emma Watson nude photo threat appears to have been the work of a viral marketing firm calling itself Rantic.com.

The ominous threat first appeared on 4chan over the weekend, sometime after the British actor and UN Women's goodwill ambassador​ launched her HeForShe campaign for gender equality at the United Nations in New York City.

The threatening message on Emmayouarnext.com has since been replaced with a message calling for 4Chan to be shut down. (Emmayouarenext.com) The threat linked to a website titled Emma You Are Next featuring a countdown clock ticking down to a suggested nude photo reveal within a number of days.

In the early hours of Wednesday, the sinister notice was replaced. Instead, the URL redirects to Rantic.com, a mysterious social media marketing company and its campaign to shut down 4chan — the image-sharing site at the centre of a number of recent celebrity nude photo leaks.

"None of these women deserve this," reads Rantic.com's splash page. "[A]nd together we can make a change."

It's not clear who is behind Rantic, or if the Harry Potter star is participating in the campaign, but a strongly worded statement on the supposed marketing firm's website claims celebrity backing.

Massive media pickup

"We have been hired by celebrity publicists to bring this disgusting issue to attention," reads a message addressed to U.S. President Barack Obama.

Emmayouarenext.com now points to an anti-4chan campaign launched by social media marketing company Rantic.com. (Rantic.com) "The recent 4chan celebrity nude leaks in the past 2 months have been an invasion of privacy and is also clear indication that the internet NEEDS to be censored."

The campaign encourages visitors to send a letter to the White House demanding government action over the nude celebrity photo leaks.

Whether the stunt can generate government action is yet to be seen, but the internet pranksters are already claiming a viral victory.

Rantic says its Watson stunt spawned massive social media pickup, generating 48 million visitors and seven million Facebook shares in a few short days.