Networks are a crucial component of information systems and businesses. This presentation demonstrates both passive and active attacks on networks that can cause havoc if they fail to implement comprehensive countermeasures. The security of Open Shortest Path First (OSPF), a popular routing protocol, will be examined. Attacks discussed include passive topology discovery, traffic redirection, man-in-the-middle, and GPU-based offline brute-force recovery of authentication keys. Some recently developed and released tools will be demonstrated in this talk. An understanding of networking fundamentals is assumed.This talk is intended for professionals who want a greater understanding of threats against local networks. They will learn how attacks can be implemented against networks that have inadequate controls, and the importance of these controls will be reinforced. It is hoped that due to this education the security of networks will improve.