Vista’s security advances may be ambitious, but they could seem ho-hum in comparison to those of Longhorn when the server OS stampedes onto the scene later this year. The last time we saw Longhorn it was still prebeta 3, but its security promise remains bright.

On the obvious side, there’s a redesigned Windows firewall. Yet another cut above the advanced Windows firewall that Microsoft released late last year, Longhorn’s firewall will combine firewall and IPSec management. The rules engine has also become smart enough to handle policy-based security, including authentication and encryption. You can even point specific rules at certain servers (such as the Active Directory server) or user groups. And you’ll be able to manage all this with new Microsoft Management Console snap-ins as well as direct support in management apps from the System Center family.

Then there’s Microsoft’s work on hardening the operating system. Hey, it only took a decade of user requests, but Microsoft seems to finally have made a real effort. Longhorn’s kernel is protected in a manner similar to Vista’s, and the OS will also support BitLocker file encryption, which will include authentication support at the chip level or the use of outside devices such as dongles. BitLocker is also built specifically to block anyone from back-dooring data by installing a guest OS or similar cracks. And speaking of physical security, Longhorn has native support for removable device installation control (which apparently goes beyond USB access), and it has a new restart manager.

On the software side, Microsoft says it has hardened Windows Services. Under Longhorn, before a service is installed, it first gets profiled for allowable actions to critical network and server resources. Using this technology, Longhorn should be smart enough to get suspicious of services that request access to naughty areas.

Finally, there’s NAP (Network Access Protection). Similar to Cisco’s NAC (Network Admission Control), this is perimeter scanning designed to ensure that every client logging on to the network is authenticated properly and adhering to security policies. Longhorn administrators can design responses to various NAP scenarios using all the usual tools: DHCP, VPN, IPSec, and so on. But although NAP sounds great on paper, it’s got more than the usual Microsoft hurdles to surmount.

NAP is a follow-up to Cisco’s NAC, so the slow rate with which Cisco has grown this technology may hurt Longhorn in the short run. Fortunately, the companies announced a joint agreement on protocols to combine NAC and NAP on a single network back in September 2006. As long as Microsoft can get customers on board, the technology should be there.

Microsoft has painted a rosy picture of Longhorn security, suggesting a bigger leap forward on the server side than on the client side. Will the promise bear out? When Longhorn enters its RTM (release to manufacturing) phase, we’ll test it and let you know.