Protecting computer networks by altering unwanted network data traffic. An Intrusion Protection System (IPS) or an Intrusion Detection System (IDS) can monitor network data traffic comprising byte information. This network security device analyzes network data traffic at the byte level to determine whether an intrusion event is present in the network data traffic. If an intrusion event is detected, the network security device alters at least a portion of the relevant byte information to prevent the occurrence of a successful intrusion event at the intended destination. This altered byte information is then passed to the destination by the network security device. If an intrusion event is not present, the network security device passes the byte information without alteration to the destination.