Purpose of the present thesis is to investigate common, but also, dangerous vulnerabilities that pose a threat to computer systems. These vulnerabilities occur, mainly, due to the absence of the development of secure programming source code. While these can easily be avoided by an attentive programmer, many programs still contain these kinds of vulnerabilities. In this document there will be described three different types of vulnerability exploits and will then be explained, with examples, how can be used in order to exploit the vulnerable systems.