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Exploring Windows XP's Security Strategy

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  1. Exploring Windows XP's Security Strategy
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Microsoft's continued definition of the security model in its operating systems continues with Windows XP. The use of authentication and Kerberos technology further accentuates the Windows XP security model. The continued development of the Microsoft security model is defined in this article.

Leveraging the lessons learned from the significant efforts adding security to Windows 2000 Professional and Server, Windows XP Professional and Home both look to be operating systems that integrate security features not previously integrated at the system level of any previous desktop OS. Certainly, the refinement of Kerberos security in the context of Windows XP is part of the more pervasive security architecture of this next-generation operating system. Think of Kerberos as being at the very basis of the XP security architecture, residing in the kernel level of the operating system. The fourth article in this series deals specifically with Kerberos and its migration from Windows 2000 to Windows XP. For now, this article will focus on the security improvements that Microsoft is actively providing in Windows XP Beta release 2.

What's New in Security Shown in Windows XP?

The security philosophy in Windows XP is actually based on the assumption that more than 80 percent of all workstations and PCs running this operating system will have a high-speed connection to the Internet. Following is a list of the new security features, which are described in detail throughout the remainder of this article:

  • Inclusion of an Internet Connection Firewall via software at the kernel level

  • Guest-only access when authentication for administrator logins fails

  • Software restriction codes for application use

  • Security improvements for servers and wireless LANs usage

  • Single login for Microsoft Passport

  • More effective and robust credential management

  • Introduction of a new file system specifically for accentuating security: Encrypting File System (EFS).

Exploring the Internet Connection Firewall in Windows XP

Because many small business and home users have increased their use of high-bandwidth connections to the Internet (including cable modems; ISDN; and in the case of small businesses, fractional T1 and full T1 lines), there's been the corresponding need for greater security than ever before. As the lower-end routers from D-Link, 3COM, and others have shown, there's a robust need for Internet security in homes and small businesses. Microsoft's inclusion of their Internet Connection Firewall is actually a packet filter that acts as a software-based checking mechanism to ensure that the only packets that are received and sent are ones authorized by the authentication policies of the PC or workstation running Windows XP.

The Internet Connection Filter is actually part of a broader Internet Connection Sharing host that acts as the gateway with the other systems that need access to the Internet. When enabled, the Internet Connection Firewall blocks all unsolicited connections originating from the Internet. To accomplish this, the firewall uses the logic of the Network Address Translator (NAT) to validate incoming requests for access to a network or the local host. If the network communication did not originate within the protected network, or if no port mapping was created, the incoming data will be dropped.

Internet Connection Firewall is available for the following types of connections: local area network (LAN), Point-to-Point Over the Ethernet (PTPOE), Virtual Private Network (VPN), or dial-up. Internet Connection Firewall prevents the scanning of ports and resources (file and printer shares) from external sources. For example, if someone on the Internet runs a scanning program on your public connection or attempts to connect to your system's resources, the firewall prevents release of any information from the ports and services available on your network.

Network Access Explained in Windows XP

Windows XP provides built-in security to keep intruders out by limiting anyone trying to gain access to your computer from a network to "guest" level privileges. If an intruder attempts to break into your computer and gain unauthorized privileges by guessing passwords, they will be unsuccessful (or obtain only limited, guest-level access). This is an improvement from Windows 95, Windows 98 and Windows NT, in which there is little if any true security at the authentication layer. In Windows NT, the security model became part of the kernel mode, and has authentication, which is now reflected in Windows 2000.

Software Restriction Codes for Application

As part of the broader reliability features of Windows XP, there's also a focus on defining software restriction codes for using specific applications users choose to limit access to. Software restriction policies in Windows XP provide a transparent way to isolate and use untrusted, potentially harmful code in a way that protects you against various viruses, trojans, and worms that are spread through e-mail and the Internet. These policies allow you to choose how you want to manage software on your system: Software can be "strictly managed" (you decide how, when, and where code gets executed), or it can be "unmanaged" (specific code is prohibited from executing).

By executing untrusted code and scripts in a segregated area (known informally as the sandbox), you get the benefit of untrusted code and scripts that prove to be benign, whereas the tainted code is prevented from doing any damage. For example, untrusted code would be prevented from sending e-mail, accessing files, or performing other normal computing functions until verified as safe. There's the concept of a dedicated memory pool in the device verifier that keeps driver code separate from the broader configuration until the implications of the driver's installation can be seen.

Software restriction policies protect against infected e-mail attachments. This includes file attachments that are saved to a temporary folder as well as embedded objects and scripts. You're also protected against URL/UNC links that can launch Internet EXPlorer, or another application, and download a Web page with an untrusted embedded script. ActiveX!" controls downloaded from the Web are also monitored and neutralized, if necessary.

Security Improvements for Servers and Wireless LANs Usage

Secure Wireless/Ethernet LAN enhances your ability to develop secure wired and wireless local area networks (LANs). With Secure Wireless/Ethernet LAN, a computer will not usually be able to access the network until the user logs on. However, if a device has "machine authentication" enabled, that computer can obtain access to the LAN after it has been authenticated and authorized by the IAS/RADIUS server.

Secure Wireless/Ethernet LAN in Windows XP implements security for both wired and wireless LANs that are based on IEEE 802.11 specifications. This process is supported by the use of public certificates that are deployed by auto-enrollment or smart cards. This enables access control for wired Ethernet and wireless IEEE 802.11 networks in public places such as malls or airports. This IEEE 802.1X Network Access Control security feature also supports authentication of computers within the Extensible Authentication Protocol (EAP) operating environment.

IEEE 802.1X enables an administrator to assign permission for a server to obtain authenticated access to both wired Ethernet and wireless IEEE 802.11 LANs. So, if a server is placed on a network, the administrator would want to ensure that it can access the network only if it has been successfully authenticated. For example, access to a conference room could be provided to only specific servers and denied to others.

Single Login for Microsoft Passport

Windows XP, the Passport authentication protocols have been added to WinInet, the DLL that allows your computer to retrieve data from different locations, allowing the OS to transparently use Passport authentication. If you have a Microsoft Passport account, you can automatically use Passport for numerous tasks such as logging into any Web site that supports Passport or purchasing products on participating Web sites.

More Effective and Robust Credential Management

The Credential Management feature provides a secure store of user credentials, including passwords and X.509 certificates. This provides a consistent, single sign-on experience for users, including roaming users. If you access an application within a company network, your first attempt requires authentication and you're prompted to supply a credential. After providing this credential, it will be associated with the requesting application. In future access to this application, the saved credential will be reused without having to re-enter the credential. It has three components: the Credential Manager itself, which provides secure storage for credentials; the Credential Collection User Interface, which provides a set of APIs that prompt the user for credentials; and the Keyring, which allows users to add, remove, and modify credentials in Credential Manager.

Encrypting File System (EFS)

The Encrypting File System (EFS) is based on public-key encryption, and takes advantage of the CryptoAPI architecture in Windows XP. The default configuration of the EFS requires no administrative effort—you can begin encrypting files immediately. EFS automatically generates an encryption key pair for a user if one does not exist.

EFS can use either the expanded Data Encryption Standard (DESX) or Triple-DES (3DES) as the encryption algorithm. Encryption services are available from Windows Explorer.

You encrypt a file or folder by setting the encryption property for files and folders, just as you set any other attributes, (such as read-only, compressed, or hidden). If you encrypt a folder, all files and subfolders created in or added to the encrypted folder are automatically encrypted. It is recommended that you encrypt at the folder level.

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