San Francisco, May 17 (IANS): Facebook is in the process of restoring a number of groups that were affected by "sabotage" and were erroneously removed, the media reported.

Facebook removed several groups from the platform after detecting content that violated its policies, but an investigation revealed that the content had been "posted to sabotage legitimate, non-violating groups", The Verge reported on Thursday quoting a spokesperson of the social network.

Facebook did not confirm who were the people behind the attack, but said that it is working to restore any groups affected and to "prevent this from happening again."

The attack came to light earlier this week when a popular meme account on Facebook known as Crossovers Nobody Asked For (CNAF) was suddenly shut down.

Members of the group later discovered that a group known as Indonesian Reporting Commission (IReC) celebrated CNAF's page being taken down, triggering suspicion that this group was behind the attack.

The Indonesian Reporting Commission gets groups and pages suspended through posting questionable content and mass reporting it, The Verge reported.

While the attack mainly affected a network of popular meme pages and groups, the incident exposed the vulnerability of Facebook's moderation approach.

As the news of the group shutdown spread quickly, it led to thousands of popular Facebook pages to switch from "private" to "secret" mode - which makes them virtually undetectable - as a measure to prevent themselves from being shut down, said the report.