Scarlett Johansson said fighting against “deepfake” porn videos, in which someone’s face is superimposed onto a clip they didn’t actually appear in, has become a “lost cause.” The “Avengers” star commented in a Sunday Washington Post story about how artificial intelligence software is being used to create increasingly realistic-looking fake porn videos — and how woman are inordinately targeted. One bogus video, with what is falsely described as “leaked” footage of Johansson, has been viewed more than 1.5 million times on a popular porn site.

Doctored photos can easily create false memories. What happens when there’s fake video?

FOR WEEKS, COMPUTER scientist Siwei Lyu had watched his team’s deepfake videos with a gnawing sense of unease. Created by a machine learning algorithm, these falsified films showed celebrities doing things they'd never done. They felt eerie to him, and not just because he knew they’d been ginned up. “They don’t look right,” he recalls thinking, “but it’s very hard to pinpoint where that feeling comes from.”

Computer-generated videos are getting more realistic and even harder to detect thanks to deep learning and artificial intelligence. As WSJ’s Jason Bellini finds in this episode of Moving Upstream, these so-called deepfakes can be playful, but can also have real, damaging consequences for people’s lives.

‘Don’t believe everything you see on the internet’ is pretty standard advice, but it’s getting harder than ever to distinguish the real from the fake. A new algorithm from Nvidia could muddy the waters further by generating completely made-up human faces that are almost indistinguishable from the real thing.