Although many organisations make use of operating systems (OS) such as Microsoft Windows, in its various flavours, or the enterprise-level variations of UNIX, in recent years a new OS has appeared to challenge the market domination of these systems – the open source platform, Linux. Linux has a mixture of advantages and disadvantages in comparison to its more well established competitors, for example whilst it is lower in cost to run and more adaptable in terms of being modified to respond to changing conditions (such as being modified to prevent a hacker attack), it can also be more difficult to operate, requiring a higher level of knowledge from administrators.