COS is a Linux kernel-based mobile operating system developed in China mainly targeting mobile devices, tablets and set top boxes. COS stand for China Operating system and is being developed by the Institute of Software at the Chinese Academy of Sciences (ISCAS) together with Shanghai Liantong Network Communications Technology to compete with foreign operating systems like iOS and Android. The operating system is based on Linux but the platform is closed source. Security and the risk of back doors in devices from foreign vendors are some of the main motivations for COS. Android had almost 90% of the smart phone market when COS was introduced and Apple most of the remaining market share. COS looks very similar to Android and has its own Application Portal much like Android Market and iOS App Store.