In a message on Tuesday, the hackers allude to attacks on movie theaters showing "The Interview."
Due to open Dec. 25, the movie is a comedy about celebrity TV interviewers sent to North Korea on a secret mission to kill leader Kim Jong Un. It has some speculating that North Korean hackers were behind the attack on Sony.
"We will clearly show it to you at the very time and places 'The Interview' be shown, including the premiere, how bitter fate those who seek fun in terror should be doomed to," the message said.
Whoever wrote the email doesn't appear to know that the premiere of the movie already happened, last week in Los Angeles, without incident.
"The world will be full of fear. Remember the 11th of September 2001," it said. "We recommend you to keep yourself distant from the places at that time. (If your house is nearby, you'd better leave.)"
The threat, whether credible or not, grabbed the attention of some media outlets.
Variety screamed "Sony Hackers Threaten 9/11 Attack on Movie Theaters That Screen 'The Interview'," The Daily Beast said, "Sony Hackers Issue 9/11 Warning" and The Verge turned the threat toward moviegoers rather than theaters and reported, "Sony hackers threaten terror attacks against people who see The Interview in theaters."
The message was reportedly accompanied by what appears to be a new leak of documents, this time related to Michael Lynton, CEO of Sony Entertainment.
Hackers had previously promised they would release a "Christmas gift" and said the latest documents were the first part of that data dump.
It's been almost three weeks since Sony Pictures was attacked and gigabytes of emails, corporate secrets and other documents were stolen from the company.
The FBI is investigating the case but so far has made no statement on the probe. The latest threats will add urgency to the hunt for those responsible and likely lead to additional charges to anyone who is eventually caught.
Martyn Williams covers mobile telecoms, Silicon Valley and general technology breaking news for The IDG News Service. Follow Martyn on Twitter at @martyn_williams. Martyn's e-mail address is martyn_williams@idg.com