A network security interface component comprising: a first network interface connected to a secure or private network of sensors; a second network interface separate from the first network interface, the second network interface connected to a public network; a unidirectional connection connecting the first network interface to the second network interface; and an authentication module connected between the first network interface and the unidirectional connection, wherein the unidirectional connection is configured to allow data transfer from the first network interface to the second network interface via the unidirectional connection and to prevent data transfer from the second network interface to the first network interface via the unidirectional connection, wherein the authentication module is configured to add authentication data to data received at the first network interface by which the data received at the first network interface can be authenticated, wherein authenticated data received means that the authentication data associated with the data received has been verified so that a recipient of the authenticated data can be sure that the data originated from a sensor of the network of sensors and that it has not been tampered with, characterized in that the authentication module is configured to identify data received at the first network interface which does not comprise authentication data and to add authentication data to the identified data received at the first network interface which does not comprise authentication data, and that the authentication module is configured to identify data received at the first network interface which comprises authentication data and to allow the identified data received at the first network interface which comprises authentication data to be transmitted via the unidirectional connection to the second network interface without adding authentication data. a first network interface connected to a secure or private network of sensors; a second network interface separate from the first network interface, the second network interface connected to a public network; a unidirectional connection connecting the first network interface to the second network interface; and an authentication module connected between the first network interface and the unidirectional connection, wherein the unidirectional connection is configured to allow data transfer from the first network interface to the second network interface via the unidirectional connection and to prevent data transfer from the second network interface to the first network interface via the unidirectional connection, wherein the authentication module is configured to add authentication data to data received at the first network interface by which the data received at the first network interface can be authenticated, wherein authenticated data received means that the authentication data associated with the data received has been verified so that a recipient of the authenticated data can be sure that the data originated from a sensor of the network of sensors and that it has not been tampered with, characterized in that the authentication module is configured to identify data received at the first network interface which does not comprise authentication data and to add authentication data to the identified data received at the first network interface which does not comprise authentication data, and that the authentication module is configured to identify data received at the first network interface which comprises authentication data and to allow the identified data received at the first network interface which comprises authentication data to be transmitted via the unidirectional connection to the second network interface without adding authentication data. <EOS>