Facebook vowed last January that it would crack down on hoax news stories with an improved News Feed feature that allowed users to flag them as fake. However, as BuzzFeed News reported this week, these false viral stories are still alive and well on the site.

Some of the major fake news distributors, like National Report, saw engagement take a hit in 2015. However, according to data analyzed by BuzzFeed News, those figures were already rebounding by the end of last year.

Of course, Facebook has good reason to want to get rid of these sites. They take advantage of users’ curiosity by getting them to click to a link, generating ad revenue for the hoax story provider. Not only do these fakes go viral naturally, but they’re also often promoted by celebrities and radio stations. This lends them a convincing legitimacy.

All in all, it may be an uphill battle for Facebook to entirely rid itself of fake news. As National Report creator Allen Montgomery explained, even if Facebook shuts down one provider, there will always be more waiting to take its place.

“They can shut down National Report. Of course they can do that,” he said. “But I could have 100 domains set up in a week, and are they going to stop every one of those? Are they now going to read content from every site and determine which ones are true and which ones are selling you a lie? I don’t see that happening. That’s not the way that the Internet works.”