"Black Hole" Router Detection: Windows XP SP3 includes improvements to black hole router detection (detecting routers that are silently discarding packets), turning it on by default.
This is a worthwhile hardening of the Windows IP stack. It will help routers detect, in advance, the shortest path to send a hefty number of datagram's.
Network Access Protection: NAP is a policy enforcement platform built into Windows Vista, Windows Server 2008, and Windows XP SP3 with which you can better protect network assets by enforcing compliance with system health requirements. Using NAP, you can create customized health policies to validate computer health before allowing access or communication; automatically update compliant computers to ensure ongoing compliance; and optionally confine noncompliant computers to a restricted network until they become compliant.
This is NAP making its debut on Windows XP. Much like Cisco NAC, NAP helps with security policy enforcement at the endpoint.
Descriptive Security Options User Interface: The Security Options control panel in Windows XP SP3 now has more descriptive text to explain settings and prevent incorrect settings configuration.
Despite the name of this feature being, itself, so nondescriptive, translated it means Microsoft will try to better communicate the meaning of security settings to you. Yeah, right.
Enhanced security for Administrator and Service policy entries: In System Center Essentials for Windows XP SP3, Administrator and Service entries will be present by default on any new instance of policy. Additionally, the user interface for the Impersonate Client After Authentication user right will not be able to remove these settings.
I'm not exactly sure what new benefit, or higher level of security, this will provide. Perhaps it should be run through the "Descriptive Security Options User Interface."
Microsoft Kernel Mode Cryptographic Module: Fips.sys is a FIPS 140-1 Level 1-compliant, general purpose, software-based, cryptographic module in the kernel mode level of the Windows operating system. It runs as a kernel mode export driver (a kernel-mode DLL) and encapsulates several different cryptographic algorithms in an easy-to-use cryptographic module accessible by other kernel mode drivers. It can be linked to other kernel mode services to permit the use of FIPS 140-1 Level 1-compliant cryptography.
This was first available in Vista. I lost this functionality when I downgraded back to XP. Soon, I'll have it again . . .
Windows Product Activation: As in Windows Server 2003 SP2 and Windows Vista, users can now complete operating system installation without providing a product key during a full, integrated installation of Windows XP SP3. The operating system will prompt the user for a product key later as part of Genuine Advantage. As with previous service packs, no product key is requested or required when installing Windows XP SP3 using the update package available through Microsoft Update. Note: This update affects the installation media only and is not a change to how activation works in Windows XP.
This is good news. They're not making the activation process worse. I had the pleasure of enduring XP activation over the weekend, as I transferred my XP install from Boot Camp to Parallels. Perhaps it was the new Voice Activated Windows Product Activation User Interface Telephony Service, but reading the product key to the voice activated system actually was more convenient than having to go through all of that rigmarole with a live person.
More information on Windows XP SP3 is available here.