NT SECURITY Introduction Security features of an operating system revolve around the principles of “Availability,” “Integrity,” and Confidentiality. For a system to be “Confidential,” it must provide features which control data access to those persons who require it for the business process or function. The information must be available to users this is the key concept surrounding “Availability.” The “Integrity” of the data involves the requirement that the data is in the form that is needed for the business process. The designers of NT 4.0 made a conscious effort to realize these features in this network operating system.

Introduction Microsoft Windows NT 4.0 features a fully pre-emptive 32-bit multitasking operating system that is scalable across enterprise level networks with diverse clients. It supports Novell, DOS, Windows 95, Unix and Apple Workstation. This system allows for the granular control of resources, as well as strong authentication and encryption. It has many security features that make it a more stable platform than its predecessors, and yet retains the familiar Windows 95/98 interface. Many networking features have been build into both the server and workstation version of this product, but NT server has many more features than the workstation variant.

NT System Identification The NT token for users is known as the System Identification or SID. It is based on a combination of the user identification, account domain, process up time, password, time, and a unique hashing function that is specific to NT. This method guarantees that a user with a given name, and a given password will be almost certain to be uniquely identified by the system. The SID is the real basis for access and permission in NT. SIDs are not re-used with identical accounts in this operating system.

NT IDENTIFICATION AND AUTHENTICATION The User in the NT environment is identified by some arrangement of characters. The authentication mechanism for each identified user is a configurable password. Specific constraints may be applied to individual user identification including; length of passwords, times of access, duration of password authenticity, rotation, and even the composition of the password. The individual user and password identification is used by the NT operating system to generate a unique token that is referenced for each process initiated by the user.

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NT ACCOUNT CONTROLS User accounts that are part of the default installation of NT server include, Administrators, Users, Guests, Backup Operators, Replicators, Print Operators, Account Operators, and Server Operators. Each type of user is limited in the privileges that may be exercised on the system. Users may be either global accounts (able to access the server remotely), or local accounts. Accounts may be customized to a large degree beyond these default accounts.

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NT SECURITY OBJECTS Security for NT is included in many fundamental aspects of the operating system. These aspects are represented as objects and the security subsystem maintains the permissions related to the objects contained in the system. Account rights may be as specific as an individual user account, or may be applied to a group of users who have been granted identical privileges.

NT SECURITY COMPONENTS NT features a security subsystem that contains many separate components to enhance the security of the product. These features include; Local Security Authority (LSA), the Security Reference Monitory, (SRM), and the Security Account Manager (SAM). Each component of the security subsystem has a role in maintaining the confidentiality, integrity and availability of the operating system. The rights or ability of a user to gain access to a file, application, or system resource, is dependent on the rights granted to the individual accounts by the system administrator. NT is able to control user access to file and directories, operating system processes and programs, as well as the systems of NT itself.

ACE/ACL/LSA CONTROLS The object in the NT environment is closely related to the Access Control Entry. This is an individual list of permissions and attributes that are featured by a specific object. The combination of all system ACE permissions and attributes is known as the system Access Control List (ACL). Each system maintains a database of account permissions that is referenced upon system access (log-in). This database is the Security Account Manager, and it retains information such as passwords and account information. The Local Security Authority (LSA) to validate the request of individual users based on the ACL.

SRM The functional portion of the SAM and LSA is the Security Reference Monitor, which is based, in the very core of the operating system or the kernel. All instantiations of processes, and access are actually verified by the SRM. The SRM is used for system calls, as well as user access requests. This allows individual services of the operating system to verify access requests through the SRM.

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WORKGROUP MODELS In a workstation model, NT workstation is used as the authenticating authority for the resources on the host computer. If there are 10 computers sharing resources then each computer must be authenticated individually for each resource to be shared. This would mean that there would be a potential of 90 different passwords in all (10 * 9) for every combination of sharing. NT server offers centralization of these services, and is capable of managing accounts within or across Domains. The workgroup model becomes very difficult to manage after the addition of only a few computers.

DOMAIN MODELS NT server is capable of the authentication of users across a single Domain. The Primary Domain Controller is able to authenticate individual users, as well as replicate SAM accounts to secondary controllers known as Backup Domain Controllers. This central management of users is a key feature of NT, and may be extended across domains by the use of trust relationships. The server in NT is generally given one of three roles, the Primary Domain Controller, the Backup Domain Controller, and the Stand-alone server. PDC and BDC servers may exchange roles due to a hardware failure, and continue the authentication of users with little or no problem

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FILE SYSTEM/ACCESS CONTROL NT is capable of very fine access control of users. Individual files can be controlled through the use of the NT file system (NTFS). This allows for the control of access to files and programs, as well the extension of permissions by persons with access. This means that the system administrator may control files copied from one directory to another. User rights are generally kept to those absolutely required by the system. This allows for a clear separation of power within the system and the enforcement of minimal privileges. These are key components that serve as the foundation of good security practices.

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NT ENCRYPTION AND AUDITING NT confidentiality is supported by a number of encryption features that are a part of the operating system. Domestic versions of NT support up to 128-bit encryption in addition to encrypted authentication of remote access services. Export versions of NT support less robust encryption features. In addition to the encryption and fault-tolerance features of the operating features, system auditing is supported for security, applications, and system events. This is a method of recording system failures, access attempts, and changes in the configuration of files. The audit features allow for very close monitoring of the allocation and alteration of resources

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NT FAULT TOLERANCE NT offers several features that contribute to the integrity of the system. Raid configurations that are based on software solutions, tape back-up based on software, and multiple processors. Raid types supported by NT software include disk duplexing and disk striping. The use of redundant disks contributes to the availability of the system and the integrity of the data being processed

Sources Windows NT 4.0 Server Security Guide (Prentice Hall Series on Microsoft Technologies, Gonsalves, Marcus Windows NT Server Networking Guide, Microsoft Press1996