Network forensics is an extension of the network security model which traditionally emphasizes prevention and detection of network attacks. It addresses the need for dedicated investigative capabilities in the current model to allow investigating malicious behavior in networks. It helps organizations in investigating outside and inside network attacks. It is also important for law enforcement investigations. In this paper, various aspects of network forensics are reviewed as well as related technologies and their limitations. Also, challenges in deploying a network forensics infrastructure are highlighted.