The hacking group Anonymous is allegedly threatening to "destroy" Facebook on 5 November, accusing the social networking site of spying on users, cooperating with authoritarian governments and abusing people's privacy.
The threat is contained in a video that was posted on YouTube on July 16, which has now been viewed more than 700,000 times and has been getting more comments by the minute.
But the threat has not been posted on Anonymous' prolific Twitter feed or its blog, anonops.blogspot.com, leading some experts to wonder if it really originates with the group or is a fake.
The video "was posted almost a month ago and yet has not been widely publicised, or publicised at all, on the usual Anonymous channels, the Twitter profiles that appear to be associated are inactive," wrote Rik Ferguson, director of security research and communication at Trend Micro, on a company blog.
Ferguson noted that a Twitter profile associated with the threat also appears to be inactive.
In the video, Anonymous claims that Facebook was working with authorities in Egypt and Syria in order to spy on people and was also allegedly providing information to security companies about users on the site. The settings on Facebook intended to make certain information more private are a "delusion," the group claimed.
"Kill Facebook for the sake of your own privacy," according to the scrambled voice on the two-minute video.
A Facebook spokeswoman contacted in London said the company had no comment.
Anonymous and an affiliated group called Lulz Security have lead numerous hacking campaigns against organizations, businesses and governments whose policies they find offensive. One of their tactics is to conduct distributed denial-of-service attacks, which involve bombarding a website with traffic in an attempt to cause the website to stop responding.
The groups have also hacked into servers and stolen information, posting it publicly. Their targets over the last few months have included the CIA, PBS.org, Fox.com and the Serious Organised Crime Agency.