There is no denying the fact that with the widespread usage of computers and the Internet in our daily lives, security of information and data has gained increased attention. Information stored in electronic form is more susceptible to being leaked to unauthorized individuals intentionally or without intent. One of the major reasons for this breach of security has been attributed to proprietary software whose source is available only to the company which made it. Thus you have no surety that the proprietary and pre-compiled software has no hole to help an individual break security of your computer or network. Philosophy of free and open source software as against this provides everyone an opportunity to view the source code for any possible vulnerabilities and compile and change it according to ones need. This paper discusses this philosophy in length with some examples and also some open source tools that help maintain computer and Internet security.