Network forensics is a sub-branch of digital forensics relating to the monitoring, capture, recording and analysis of computer network traffic for the purposes of information gathering, legal evidence, or intrusion detection in order to discover the source of security attacks or other problem incidents. Unlike other areas of digital forensics, network investigations deal with volatile and dynamic information. Network traffic is transmitted and then lost, so network forensics is often a pro-active investigation.
Network forensics generally has two uses. The first, relating to security, involves monitoring a network for anomalous traffic and identifying intrusions. An attacker might be able to erase all log files on a compromised host; network-based evidence might therefore be the only evidence available for forensic analysis. The second form relates to law enforcement, in this case analysis of captured network traffic can include tasks such as reassembling transferred files, searching for keywords and parsing human communication such as emails or chat sessions for further investigation.