National Research Institutes of Advanced Industrial Science and Technology (AIST) is governed by the Ministry of Economy Trade and Industry of Japanese government. The Information Technology Research Institute of AIST has noticed that the open source software approaches are important issues to have high quality and secure software. In this paper, after we have shown four projects of open source software carried out at AIST, we show a typical and simple security problem named "cross site scripting" of Web servers. If the application software for the Web server were opened, this security hole would be quickly fixed because the problem is very simple and the way to fix is quite easy. Then we show several reports on Linux operating system of using governmental computer network infrastructures. We see that a lot of countries are considering using Linux and its application software as their infrastructures. Because of the national securities and the deployment costs AIST is now planning to use Linux office applications in order to assess the feasibility of using open source software as an important infrastructure.