I feel that the fact that Windows is the most popular OS is the reason for this conclusion. If Linux had the kind of market share that Microsoft does, then the situation would be reversed, with Linux being declared a threat to National Security. I feel that monopolies are bad for everyone in nearly every case... ie: Standard Oil, AT&T, etc, etc. They increase prices, and stagnate development. In summary, Microsoft is a comparitively secure OS, and if any other OS had the same share of the market, they would be criticized in the same way.