Facebook revealed details on an incident earlier this week that caused some developer applications to accidentally go offline for several hours. The social network confirmed that on Tuesday, while running automated systems to identify and disable malicious apps, the tools inadvertently disabled some legitimate third-party apps. Facebook did not say how many apps were affected.

"Occasionally we detect an attack that requires us to augment those automated systems," said Eugene Zarakhovsky, software engineer at Facebook, in a blog post. "Specifically, we identify a malicious pattern, find all the apps that match the pattern, and then disable those apps. This normally results in thousands of malicious apps being disabled and improves our automated systems' ability to detect similar attacks in the future."

Facebook said that in this instance, it began with a broad detection pattern that correctly matched thousands of malicious apps. The problem was that it also identified and labeled legitimate apps as malicious. When it detected the error, Facebook said it stopped the process and worked to restore access. This took longer than expected because "of the number of apps and bugs related to the restoration of app metadata."