The Ransomware Protection app makes use of this characteristic. It detects common file names used by ransomware and responds by blocking further uploads and warning the user and administrator, who can then take action. As the sync client is constantly syncing, this should leave very little window between the last legitimate modification of user data and the malicious activity. However, if something made it through, users can still rely on the ability to restore older versions of files on the server.
The solution offered can not be taken as a 100% protection against ransomware. Some ransomware uses random filenames and very generic terms for the instruction files, thus offering little opportunity for detection and prevention. New ransomware also shows up regularly. However, an estimated 95% of the current ransomware can be caught and partially or fully stopped in its tracks. Neither the developer nor Nextcloud GmbH nor Webo.hosting give any guarantee that your files can not be affected by another way.