Embodiments of the present disclosure provide a method, a device and a computer program for data backup. A method of backing up data comprises: in response to receiving, from an application system, a request for backing up first data, storing the first data into a first backup node; generating first metadata corresponding to the first data, the first metadata comprising first digest information of the first data; storing the first metadata into a block chain system to which the first backup node belongs; and verifying integrity of the first data stored in the first backup node with the first metadata stored in the block chain system. By utilizing a block chain system, the embodiments of the present disclosure ensure that data backed up are protected from being tampered with.