The network has been playing a vital role in many aspects of lives such as security, health academics, etc it, therefore, requires attention due to the growing menace of cybercrime globally. This paper studied the threats posed to computing devices on network; Countermeasures as well as the technical consequences that stem from the threats. The work reviewed previous researches discussed different threats posed to networks and identified various defense mechanisms. The study found that businesses and governments have been affected seriously by network threats, causing loses and reputation. its also observed that no single countermeasure can absolutely solve the problems of network security. in addition,the network security is moving from biometric to an immune system that can act collectively in fighing any attack. Lastly, the research made some recommendations for the way forward.