Zyxel ZyWALL USG 50 Network Security/Firewall Appliance - 8 Port. The ZyWALL USG (Unified Security Gateway) 50 is the inch third generationinch ZyWALL featuring an all-new platform. It provides greater performance protection as well as a deep packet inspection security solution for small businesses to enterprises alike. It embodies a Stateful Packet Inspection (SPI) firewall, Anti-Virus, Intrusion Detection and Prevention (IDP), Content Filtering, Anti-Spam, and VPN (IPSec/SSL/L2TP) in one box. This multilayered security safeguards your organization"s customer and company records, intellectual property, and critical resources from external and internal threats.