Saturday, May 17, 2008

Windows Server 2008 Security Improvements

Security problems have plagued Microsoft since the Windows inception, but only in the last few years, as more people have become connected, have those flaws been exploited by malcontents. Indeed, some of the vulnerabilities in products that we see patches for on "Patch Tuesdays" are the results of poor design decisions. These types of flaws are the ones Microsoft is hoping to stamp out in the release of Windows Server 2008. You'll see quite a bit of change to the architecture of services in Windows Server 2008, including increasing the number of layers required to get to the kernel, segmenting services to reduce buffer overflows, and reducing the size of the high-risk, privileged layers to make the attack surface smaller.

While fundamentally changing the design of the operating system, the Windows Server 2008 team has also included several features designed to eliminate security breaches and malware infestations, as well as capabilities meant to protect corporate data from leakage and interception. Let's take a look at some of the improvements.

Operating System File Protection

A new feature currently known as operating system file protection ensures the integrity of the boot process for your servers. Windows Server 2008 creates a validation key based on the kernel file in use, a specific hardware abstraction layer (HAL) for your system, and drivers that start at boot time. If, at any subsequent boot after this key is created, these files change, the operating system will know and halt the boot process so you can repair the problem.

Operating system file protection also extends to each binary image that resides on the disk drive. OS file protection in this mode consists of a filesystem filter driver that reads every page that is loaded into memory, checking its hashes, and validating any image that attempts to load itself into a protected process (processes that are often the most sensitive to elevation attacks). These hashes are stored in a specific system catalog, or in an X.509 certificate embedded within a secure file on the drive. If any of these tests result in failure, OS file protection will halt the process to keep your machine secure. This is active protection against problematic malware.


The need for drive encryption has been a popular topic in a lot of security channels lately, and in both Windows Vista and Windows Server 2008 Microsoft has risen to the call by developing a feature called BitLocker. BitLocker is designed especially for scenarios where a thief may gain physical access to a hard drive. Without encryption, the hacker could simply boot another operating system or run a hacking tool and access files, completely bypassing the NTFS filesystem permissions. The Encrypting File System in Windows 2000 Server and Windows Server 2003 went a step farther, actually scrambling bits on the drive, but the keys to decrypt the files weren't as protected as they should have been. With BitLocker, the keys are stored within either a Trusted Platform Module (TPM) chip on board your system, or a USB flash drive that you insert upon boot up.

BitLocker is certainly complete: when enabled, the feature encrypts the entire Windows volume including both user data and system files, the hibernation file, the page file, and temporary files. The boot process itself is also protected by BitLocker—the feature creates a hash based on the properties of individual boot files, so if one is modified and replaced by, for example, a Trojan file, BitLocker will catch the problem and prevent the boot. It's definitely a step up from the limitations of EFS, and a significant improvement to system security over unencrypted drives.

Device Installation Control

Another security problem plaguing businesses everywhere is the proliferation of the USB thumb drive. No matter how securely you set your permissions on your file servers, no matter how finely tuned your document destruction capabilities are, and no matter what sort of internal controls you have on "eyes-only" documentation, a user can simply pop a thumb drive into any open USB port and copy data over, completely bypassing your physical security. These drives often contain very sensitive information that ideally should never leave the corporate campus, but they're just as often found on keychains that are lost, inside computer bags left unattended in an airport lounge, or in some equally dangerous location. The problem is significant enough that some business have taken to disabling USB ports by pouring hot glue into the actual ports. Effective, certainly, but also messy.

In Windows Server 2008, an administrator will have the ability to block all new device installs, including USB thumb drives, external hard drives, and other new devices. You can simply deploy a machine and allow no new devices to be installed. You'll also be able to set exceptions based on device class or device ID—for example, to allow keyboards and mice to be added, but nothing else. Or, you can allow specific device IDs, in case you've approved a certain brand of product to be installed, but no others. This is all configurable via Group Policy, and these policies are set at the computer level.

Windows Firewall with Advanced Security

The Windows Firewall version included with Windows Server 2003 Service Pack 1 was exactly the same as that included in Windows XP Service Pack 2. Microsoft bundled that firewall with Service Pack 1 as a stopgap measure—deploy this firewall now, Microsoft said, so you will be protected, and we will work to improve the firewall in the next version of Windows.

That time is here. The new Windows Firewall with Advanced Security combines firewall and IPsec management into one convenient MMC snap-in. The firewall engine itself has been rearchitected to reduce coordination overhead between filtering and IPsec. More rules functionality has been enabled, and you can specify explicit security requirements such as authentication and encryption very easily. Settings can be configured on a per-AD computer or user group basis. Outbound filtering has been enabled; there was nothing but internal filtering in the previous version of Windows Firewall. And finally, profile support has been improved as well—on a per-computer basis, there is now a profile for when a machine is connected to a domain, a profile for a private network connection, and a profile for a public network connection, such as a wireless hotspot. Policies can be imported and exported easily, making management of multiple computers' firewall configuration consistent and simple.

Network Access Protection

Viruses and malware are often stopped by software defenses before they can run within a user's session, but the ultimate protection would be if they never even got access to the network. In Windows Server 2008, Microsoft has created a platform whereby computers are examined against a baseline set by the administrator, and if a machine doesn't stack up in any way against that baseline, that system can be prevented from accessing the network—quarantined, as it were, from the healthy systems until the user is able to fix his broken machine. This functionality is called Network Access Protection.

NAP can be broken down into three key components:

Health policy validation

Validation is the process wherein the machine attempting to connect to the network is examined and checked against certain health criteria that an administrator sets.

Health policy compliance

Compliance policies can be set so that managed computers that fail the validation process can be automatically updated or fixed via Systems Management Server or some other management software, as well as by Microsoft Update or Windows Update.

Limited access

Access limiting can be the enforcement mechanism for NAP. It's possible to run NAP in monitoring-only mode—which logs the compliance and validation state of computers connecting to the network—but in active mode, computers that fail validations are put into a limited-access area of the network, which typically blocks almost all network access and restricts traffic to a set of specially hardened servers that contain the tools most commonly needed to get machines up to snuff.

Keep in mind that NAP is only a platform by which these checks can be made—pieces of the puzzle are still needed after deploying Windows Server 2008, including system health agents (SHAs) and system health validators (SHVs) that ensure the checks and validations are made on each individual client machine. Windows Vista ships with default SHAs and SHVs that can be customized.

*.* Source of Information : O'Reilly Windows Server 2008: The Definitive Guide

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