The issue of information security has attracted increasing attention in recent years. In network attack and defense scenarios, attackers and defenders constantly change their respective strategies. Given the importance of improving information security, a growing number of researchers are now focusing on how to combine the concepts of network survivability and protection against malicious attacks. As defense resources are limited, we propose effective resource allocation strategies that maximize an attacker?s costs and minimize the probability that the "core node" of a network will be compromised, thereby improving its protection. The two problems are analyzed as a mixed, nonlinear, integer programming optimization problem. The solution approach is based on the Lagrangean Relaxation method, which solves this complicated problem effectively. We also evaluate the survivability of real networks, such as scale-free networks.