Network security threats and defense

As we are already into the 21st century our society heavily relies on the Internet in several fields such as economics, politics, military. With the increasing impact of internet on our daily lives, various security risks are brought about by system defects, hackers and so on, which greatly threaten stability of the network, incur significant financial loss economically, and, to the most extreme extent, even can be a threat to national security. Therefore, network security has become an important issue of paramount importance in the field of economics, politics, military and people’s lives. This thesis is structured as follows: it first presents the current situation of network security, for example, the various ways and forms of current common attacks are, which are the source threats brought to the network. Chapter three introduces two of the most common network attacks we usually encounter as well as the corresponding countermeasures against every specific type of DOS and man-in-the-middle attacks. Chapter four focuses on two effective defense technologies, firewall and intrusion detection systems. Chapter four and five discuss the properties and characteristics of these two technologies along with the relative deployments and models that serve different purposes and applications. The purpose of the thesis is to discuss the common network attacks and two defense technologies so as to provide clues and mitigations for the increase in the difficulty of intrusion as well as the dramatic improvement in network security with the use effective countermeasures when network attacks are launched