Abstract: Methods and data processing apparatuses are provided which enable controlling, from one data processing apparatus, access to data held (for example on a queue) at another data processing apparatus. When a requester wishes to access data held at a local data processing apparatus, a request must be sent to a remote data processing apparatus to determine the security attributes of the data (for example, retrieving queue attributes from a database). The requestor cannot access the data until the security attributes are fully determined at the local data processing apparatus, and since communication with a remote system is required to make this determination the remote apparatus is able to log the requests for data access. The security attributes are preferably an identifier of a cryptor used in compression, a compressor used in compression and an authenticator for authenticating the requestor.