it. Access to this server is then restricted to those who pay the server's owner their own subscription fee. Multiple receiver use An arguably legitimate use for card sharing is the sharing of the control word within a home network, where the subscriber is authorised by the subscription television network to decrypt their signal, using one smart card. Content providers usually provide means for viewing channels on a second smart card, provided at extra cost. An example of this is Sky Multiroom, used in the United Kingdom. However, in some cases the contract between the subscriber and the content provider implicitly or explicitly prohibits this kind of card sharing. Countermeasures Card sharing is a particular concern to conditional access providers, and their respective pay-TV companies, as well as the DVB consortium. Card sharing utilises the integral scrambling system of the DVB standard, DVB-CSA, meaning that every provider of scrambled DVB content has potential to be affected by it. In response, several counter measures have been implemented by various parties, with the aim of permanently preventing it. Technical One technical method, implemented by providers such as Irdeto and NDS, is to update the software of digital receivers provided by the subscription television service. This software implements a further decryption layer, held within the receiver. Rather than sending a plain text control word from the smart card to the receiver's microprocessor, which can be intercepted, the decrypted ECM will in fact be an encrypted control word, which can only be decrypted by a legitimate, non card sharing capable, receiver. A simpler method, used by several providers, is to simply increase the frequency of control word changes. With changes occurring as frequently as once every few seconds, extra stress is put onto the smart card sharing system, meaning that clients may be frustrated by short, frequent, missed viewing periods. Another method gaining traction is "Card pairing". Effectively linking the card with the connected device (e.g the set-top box, CAM module or TV's decoding chipset) and locking the card to be used only on that device. Legal One significant problem for internet card sharing is that the activity can be traced, through tracing of the originating IP address - though this does not identify an individual it can lead to a specific ISP and/or TV service subscription. Cases of criminal charges have been brought against card sharing hosts. In August 2009, a Liverpool man