NextCloud is your own Google Drive / OneDrive and more. They are very famous for being great, free and open source. NextCloud has issued a warning about a possible ransomware attack on enterprise users
Warning: a vulnerability in Citrix is actively being abused to attack organizations with ransomware. Be careful, update or disable your Citrix server and consider anti-ransomware technologies like our guided undo for #ransomware recovery.
They are also providing you with methods / resources to fight ransomware. Check the link below
I hope that you know a ransomware locks your files and folders and then ask you for money for the unlock key. In most cases, even if you give them the money, your data will be gone forever as it is encrypted by the hackers.