A network level virus monitoring system capable of monitoring a flow of network traffic in any of a number of inspection modes depending upon the particular needs of a system administrator. The monitoring provides an early warning of a virus attack thereby facilitating quarantine procedures directed at containing a virus outbreak. By providing such an early warning, the network virus monitor reduces the number of computers ultimately affected by the virus attack resulting in a concomitant reduction in both the cost of repair to the system and the amount of downtime. In this way, the inventive network virus monitor provides a great improvement in system uptime and reduction in system losses.