One thing I need to make clear up front is that the AlphaShield is not a NAT router. The key consequence of this is that it does not provide Internet sharing. Instead, think of it as providing, for all intents and purposes, the same protection as provided by a NAT - or more accurately NAT + SPI (Stateful Packet Inspection) router - but without requiring, or allowing, any sort of configuration of that protection.
AlphaShield's marketing material refers to three technologies that the product uses to work its Internet security magic - AlphaGAP, IP Stealth and RPA (Real-time Packet Authorization). The first just refers to the box's ability to completely stop data flow between its Internet and host computer ports, just as if you physically disconnected your computer from your broadband modem.
IP Stealth means that AlphaShield will discard any ICMP messages it receives from pings or traceroutes, just as routers do when you enable "block WAN ping response" or similarly-named capabilities. Either way, scans directed at your IP address assigned by your ISP won't receive any response and just continue looking for their next victim.
The RPA explanation in the white paper provided as part of my review material (but not available for download from the AlphaShield website) is the fuzziest of the three and appears to be the AlphaShield's real "secret sauce". But though the exact mechanics of RPA may be different, the bottom line is that it provides essentially the same level of "firewall" protection as provided by a NAT router.
The AlphaShield's packaging makes a good first impression with an informative product box and compact and nicely finished silver and charcoal plastic enclosure. Figure 1 shows that Outbound, Connection and Inbound LEDs grace the font panel - and provide the only indication of the AlphaShield's operating state. There is no software interface to view or configure, heck, the AlphaShield doesn't even have a MAC address, let alone an IP address!
Figure 1: AlphaShield front view