In some examples, a storage system creates a first copy of a data volume, and receives write requests having a specified characteristic from a host system, the write requests to write data of the data volume, where the storage system is to reject the write requests having the specified characteristic and to accept write requests without the specified characteristic. The storage system maintains metadata for the first copy of the data volume, the metadata indicating blocks of the data volume that have changed since the first copy of the data volume was created. The storage system determines, using the metadata, whether an unauthorized data encryption of the data of the data volume has occurred.