Security is gradually taking center stage. Since traditional transport systems were based solely on mechanical or electromechanical devices and closed networks, today with an increasing number of information technologies and communications devices, systems are being migrated towards new communication technologies and open protocols. Although this has increased the efficiency and reduced costs to companies, the systems have become more vulnerable to external attacks. And railway is not and exception, its infrastructure is mainly based on computers that are interconnected via wired or wireless networks and it is highly distributed, therefore railway's infrastructure is difficult to protect and it is vulnerable to cyber-attacks. This work shows an analysis about the standards used in security. A comparison with safety norms and the main reasons why security is currently not considered when developing safety critical devices are also described. Finally, an example of safety and security integration is presented.