A method for backing up data in a computer system from at least one primary data source to a secondary data source is provided. The method includes performing a full image backup on a plurality of data blocks stored by the primary data source(s). An incremental backup can then be initiated at a predetermined interval. During this incremental backup, the modification time of each file/folder at the predetermined interval can be compared to a defined time. If the modification time is earlier than the defined time, then the data blocks of that file/folder can be excluded from the incremental backup. If the modification time is later than the defined time, then the data blocks of that file/folder can be included in the incremental backup. This method can be used to provide an efficient disaster recovery using a network.