Network monitoring is a difficult and demanding task that is a vital part of a network administrator’s job. Network administrators are constantly striving to maintain smooth operation of their networks. If a network were to be down even for a small period of time, productivity within a company would decline; and in the case of public service departments the ability to provide essential services would be compromised. There are several approaches to network security monitoring. This paper provides the readers with a critical review of the prominent implementations of the current network monitoring approaches.