Nowadays many operating systems are including security features in order to prevent network attacks, and since one of the roles of the OS is to manage the resources as efficient as possible. It is imperative to investigate the protection that is provided. Therefore, the scientific significance of this thesis was to evaluate, what type of built-in defense mechanisms that different OS's had in place in order to mitigate these network attacks.;In this thesis, we considered the security of the following globally deployed computer OS's: Microsoft's Windows 7, Apple's OS X Lion, and Ubuntu 13.10. Furthermore, we also tested four server OS's: Microsoft's Server 2008 and 2012, Apple's OS X Lion Server, and Ubuntu Server 12.04, and their performance under DoS attacks. Our experimental results show that the OS's that were evaluated were found to have inadequate security protection and showed different degree of effectiveness in handling different DDoS attacks. |