A method of selecting a set of devices and distributing data to the set of devices linked by a network, each said device having at least one unique identifier comprising a string of bits or characters of a first length, the method comprising the steps of: defining, by specifying a matching key to match at least a portion of the unique identifier of each device, the set of devices to receive the data based on the at least one unique identifier; wherein the matching key corresponds to a shorter length subset of the string of the first length; the shorter length subset of the string is of a selectable length; and the selectable length of the shorter length subset of the string is larger or smaller depending on the size of the set of devices; and distributing data to the devices of the set of devices, the data including the matching key for matching the portion of the unique identifiers of the devices of the set of devices, wherein distributing the data comprises making the data available to the set of devices and subsequently making the data available to further subsets of the population of devices; the method further comprising the steps of: monitoring the response following making the data available to the set of devices, and setting the size of the further subsets based on the response; wherein the further subsets are defined by specifying the matching key to match a portion of the unique identifier of each device; wherein the size of the set of devices and the size of each of the further subsets are determined by setting the length of the matching key to match; and wherein a shorter length will match a larger number of devices. defining, by specifying a matching key to match at least a portion of the unique identifier of each device, the set of devices to receive the data based on the at least one unique identifier; wherein the matching key corresponds to a shorter length subset of the string of the first length; the shorter length subset of the string is of a selectable length; and the selectable length of the shorter length subset of the string is larger or smaller depending on the size of the set of devices; and distributing data to the devices of the set of devices, the data including the matching key for matching the portion of the unique identifiers of the devices of the set of devices, wherein distributing the data comprises making the data available to the set of devices and subsequently making the data available to further subsets of the population of devices; the method further comprising the steps of: monitoring the response following making the data available to the set of devices, and setting the size of the further subsets based on the response; wherein the further subsets are defined by specifying the matching key to match a portion of the unique identifier of each device; wherein the size of the set of devices and the size of each of the further subsets are determined by setting the length of the matching key to match; and wherein a shorter length will match a larger number of devices. monitoring the response following making the data available to the set of devices, and setting the size of the further subsets based on the response; wherein the further subsets are defined by specifying the matching key to match a portion of the unique identifier of each device; wherein the size of the set of devices and the size of each of the further subsets are determined by setting the length of the matching key to match; and wherein a shorter length will match a larger number of devices.