The subject of the thesis is “Detecting malicious code in a web server”. One of the major problems in the web is that everyone can try to attack at your server and with the majority of vulnerabilities that are found everyday in all OS the can take access to it. Our software called PyWall tries to detect malicious code that is injected to a webserver either in the core files or in the database. There are many ways an attacker can inject the backdoor and because of the lack of security awareness in many developers this can be done very easily as we will see below.