Zyxel is positioning the USG100 as a comprehensive security appliance for offices with up to 25 users. That clearly places the unit in the small business realm, a market saddled by many challenges. Small businesses have some unique needs centered on affordability and ease of use. What's more, small businesses need access to the same level of security that is commonly available to enterprises, just without the complexity. Zyxel has recognized those needs and has built the USG100 from the ground up to service the small business market, taking a different approach than many other vendors that "dumb down" their enterprise offerings to serve the small business market.

The USG100 offers a feature set that includes:

- ICSA-certified firewall (rated at 100M bps)
- Anti-virus: ( ICSA-certified Zyxel Anti-Virus and Kaspersky Lab)
- Intrusion detection and prevention
- VPN (ICSA-certified IPSec , SSL, L2TP, up to 50 tunnels); two licenses included.
- Instant messaging and peer-to-peer management
- Anti-spam
- User-aware configuration and policy engine
- Bandwidth management and traffic prioritization
- Multiple ISP link support for high availability and redundancy
- Content filtering
- Support for 3G wireless networks (High-Speed Downlink Packet Access and Evolution Data Optimized)

The physical device sports two USB ports, two 10/100/1000 Ethernet WAN ports, five 10/100/1000 Ethernet LAN ports, a serial port (for dial-up modems), an RS232 console port and a PCCard port for PCMCIA-based communications cards. The unit includes brackets for rack-mounting and a 12-volt external power brick.