The 4G of mobile networks will be a technology-opportunistic and user-centric system, combining the economical and technological advantages of various transmission technologies. As a part of its new architecture, LTE networks will implement an evolved packet core. Although this will provide various critical advantages, it will, on the other hand, expose telecom networks to serious IP-based attacks. One often adopted solution to mitigate such attacks is based on a centralized security architecture. However, this approach requires large processing and memory resources to handle huge amounts of traffic, which, in turn, causes a significant over dimensioning problem in the centralized nodes. Hence, it may cause this approach to fail from achieving its security task. In this paper, we focus on a SPAM flooding attack, namely SMTP SPAM, and demonstrate, through simulations and discussion, its DoS impact on the Long Term Evolution (LTE) network and subsequent effects on the mobile network operator. Our main contribution involves proposing a distributed architecture on the LTE network that is secure and that mitigates attacks efficiently by solving the over dimensioning problem. It is also cost-effective by utilizing ‘off-the-shelf’ low-cost hardware in the distributed nodes. Through additional simulation and analysis, we demonstrate the feasibility and effectiveness of our approach. Copyright © 2012 John Wiley & Sons, Ltd.