If you're a member of any large Facebook groups, you may have noticed that, sometime this week, a lot of them suddenly changed their status from "closed" to "secret."

This is happening because administrators of Facebook groups are worried that their groups might be invaded by bad actors who post porn or other content banned by Facebook, report that content, and, in turn, get the group deleted—a tactic known as "zuccing."

Administrators of several large Facebook meme groups told Motherboard that a group called "Indonesian Reporting Commission" had been mass-joining and reporting posts in the group Crossovers Nobody Asked For, prompting the group to get suspended for a few hours. The admins said that they took their groups "secret" out of an abundance of caution.

Closed Facebook groups require each new member to be accepted by admins, while secret Facebook groups are undiscoverable by search, meaning new members need an invitation from group admins. Though closed groups require an admin or moderator accept new members, there are still many closed groups with tens or hundreds of thousands of members. Usually prospective members need to answer a question to join a closed group, but that question can be as simple as "what color is the sky," for example. Many groups that are effectively open to everyone are technically "closed" groups because closed groups offer group administrators better moderation options.

Motherboard was able to confirm that Crossovers Nobody Asked For was temporarily suspended, but could not determine the specifics of why. A revived version of the group is now filled with memes that target Indonesian people and memes about Mark Zuckerberg, such as this one:

Though a limited number of groups seem to have been taken down, thousands of groups went secret.

"As far as I know we weren't invaded!," Felix Honeybee, an admin of Sounds Like an Elaborate Excuse to be a Furry But OK, said in a Facebook message. “Most groups have gone secret so everyone kinda saw that and someone submitted a post warning us about it so earlier this morning we decided to play it safe and close it down. I’m not sure if any groups I’m in got deleted but most of em are secret.”

According to several admins of several large groups, they learned about the supposed "Indonesian Reporting Commission" from members of their groups who posted screenshots in their groups and warned that they could have been invaded. Here are two of the screenshots that were shared with Motherboard:

The mass panic shows how quickly rumors and, possibly, localized group vandalism can spread on Facebook and become a platform-wide phenomenon.

Earlier this month, Facebook announced that the company would be prioritizing groups on its platform as a way of helping “bring people together offline.”

“We removed several Groups from Facebook after detecting content that violated our policies. We since discovered that this content was posted to sabotage legitimate, non-violating Groups," a Facebook spokesperson said in an email. "We’re working to restore any Groups affected and to prevent this from happening again.”

Krish Munot, the admin of “Subtle Asian Tech” and “HH Interview Experiences,” said in a Facebook message that he changed the privacy settings of these groups from “Closed” to “Secret” yesterday when he heard about what happened between Indonesia Reporting Commission and Crossovers Nobody Asked For.

“I made the group secret for a short while because there has been an Indonesian bot/group posting vulgar content and reporting all types of large FB groups/pages and getting them down or banned,” Munot said. “For the safety of the various group I manage, I've made it secret for a short time period. This will be undone once I know it is safe.”

Munot said that he changed the privacy settings for HH Interview Experiences back to closed today, saying that he believes that Facebook has the issue under control.

"I actually had an account lost in a similar manner. My facebook account of 8 years was essentially deactivated because everything I ever posted was reported all at once," Merkava Jones, a moderator of the Sounds Like an Elaborate Excuse to Be a Furry group said in a Facebook message. "I guess they're going after groups now. I pray every day for a mass exodus from this hellsite."