Provided are techniques for determining whether content of an object has changed. Under control of a backup system, opaque object attributes and a data identifier are received, wherein the data identifier is generated based on one or more relevant object attributes of the opaque object attributes that indicate whether at least one of the content of the object and one or more of the relevant object attributes has changed. The received data identifier is compared with a previously stored data identifier. In response to determining that the received data identifier and the previously stored data identifier do not match, it is determined that the content of the object has changed.