Missing file check in Attachment Checker is a marker to let the app know if it has been enabled in the 3rd party virus scanner.

For virus scanners with on access scanning enabled, the file may be deleted after it is uploaded into Jira, without any feedback.

Users will only find out when they try to preview or download the attachment, which will redirect them to a dead link.

The missing file check can be enabled at Attachment Checker ConfigurationVirus Scanning

acj virus scanning config.png