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Securing Tandem Systems Previous Screen Jeffrey L 84-10-15 Securing Tandem Systems Previous screen Jeffrey L. Ott Payoff Tandem computers are the systems of choice for online transaction processing in institutions worldwide. This article provides detailed guidance for securing Tandem systems, focusing on Tandem's NonStop Guardian security and the Tandem-developed security application, Safeguard. Introduction Tandem computers are employed extensively in heavy volume, OnLine Transaction Processing environments. Tandem systems can be found in 24 of the top 25 US banks; 32 of the top 50 European banks; 250 brokerage and security firms; 60 major insurance companies; and in 40of the world s busiest stock and commodities exchanges. Tandem computers run 75% of all automated teller machine transactions, 66% of all worldwide credit card transactions, and 50% of all public E-mail systems. Despite this large presence in computing environments worldwide, Tandem computers are as yet enigmatic to information security practitioners and information systems auditors. This is primarily because Tandem systems are designed with fault tolerance, low maintenance, and low overhead in mind. In many large financial institutions, only two employees provide Tandem system administration and management (i.e., perform operating system upgrades, capacity planning and tuning, and other related maintenance tasks). Compare this with the number of people generally required to support a large mainframe and it is obvious why the Tandem system is often forgotten until something specific is required of it. Tandem Computers, Inc., which developed its first fault tolerant computer in 1976, is also partially responsible for the lack of security awareness on its systems. Safeguard, the Tandem's security application, is the only security application used with the system. It was not until the company's recent D30 release of the NonStop Kernel—Tandem s operating system—and Safeguard, that Tandem pursued certification of its security environment with the National Computer Security Center (NCSC). Although Tandem's security environment does not provide the controls and granularity of more established and refined security packages, such as CA-ACF2 and RACF, it is possible to secure a Tandem system. This article addresses the various components of Tandem security, focusing on basic NonStop Guardian security, Safeguard security, and the interaction between the two. In addition, the chapter provides suggestions for minimizing risk and improving administration in a Tandem system. Tandem Architecture Basics Organizations choose Tandem computers for their OnLine Transaction Processing because of Tandem s proven fault tolerance, which is achieved through an integrated hardware and software design. All of the critical system components are mirrored, or duplicated. Tandem computers provide redundant power supplies, buses, I/O channels and disk drives—all for establishing a backup path in case the primary path is unavailable. The NonStop Kernel and fault tolerant software are written to recognize and use these alternate routing and backup paths. Tandem developed the Mackie Diagram as an aid for visualizing the layout of a system. Exhibit 1 illustrates a Mackie Diagram of a rudimentary Tandem system. Tandem systems are typically composed of two to 16 Central Processing Unit. As illustrated in Exhibit 1, CPUs numbering begins with Central Processing Unit 0 and follows from there. Each CPUs operates independently of, and cooperatively with, the other CPUs in the system. Previous screen This enables a multiple-CPU Tandem system to survive and continue processing should one or more of the CPUs fail. A high-speed interprocessor bus (IPB) connects each CPUs to the system. The bus handles the communications between each CPUs in the system, but does not handle communications between separate Tandem systems. There are two channels on the IPB—the X-channel and the Y-channel—and each has its own controller. If one of these buses were to fail or otherwise become unavailable, the remaining channel would ensure the continued processing of the system. I/O channels extend from each CPUs and are connected to dual-ported controller devices. The dual-ported controllers are accessible from one of two CPUs. Tandem disk drives are mirrored in that for every logical disk, there are two physical disk drives on the system, the primary and the mirror. A drive is generally referred to by its logical name and no distinction is made between the primary and the mirrored drive. A drive does not need to be mirrored; in fact, some organizations place nonessential data, such as test systems and data, on “broken mirrored” drives. However, should the drive fail, all data on that drive is at risk of being lost. Disk drives are also dual-ported, enabling data to be routed to that drive through one of two controllers. As illustrated in Exhibit 1, data destined for the volume $SYSTEM disk can take any one of four possible routes to reach the drive. Mackie Diagram of a Basic NonStop System Importantly, controllers do not necessarily need to be connected to two adjacent CPUs, as the controllers for the $SYSTEM disk drives are in Exhibit 1. Instead, to achieve maximum performance and load balancing, controllers can be connected between any two CPUs, as illustrated in the ASYNC controller connections. Tandem Naming Conventions The following sections outline the naming conventions for Tandem systems. Diskfile Naming. The Tandem file-naming convention is analogous to the DOS PC naming convention. Tandem volumes are analogous to PC drives; Tandem subvolumes are analogous to PC directories; and Tandem diskfiles are analogous to PC files. The Tandem system can have many volumes. On each volume, there are multiple subvolumes and, in each subvolume, there can be many diskfiles. A subvolume, however, cannot contain another subvolume. Volume names are preceded by a $ and are followed by a drive name of up to eight alphanumeric characters (e.g., $SYSTEM, $DATA01, or $AUDIT). Subvolume names are preceded by their respective volume name and can also be up to eight alphanumeric characters in length (e.g., $SYSTEM.SYSTEM,$DATA01.PRODDATA, $AUDIT.SAFE). Diskfile names also contain up to eight alphanumeric characters. A fully qualified filename will include the system name of the system that it resides on. The system name is placed before the volume designation and is preceded by a \. The system name is optional and is only required when referencing files outside of the current system. Examples of a fully qualified filename are: \NY.$SYSTEM.SYSTEM.USERID, \TEST.$DATA01.PRODDATA.USERS, and \AK1.$AUDIT.SAFE.A0000001. A properly constructed diskfile name will reference in this manner: \system.$volume.subvolume.filename. User Naming. Previous screen The Tandem naming convention for users is based on user groups and the users within the group. Names are viewed either by the numeric representation of <groupnumber>,<usernumber> or by the alphanumeric representation of <groupname>,<username>. The system tracks users by their numeric representations. There can be up to 256 user groups and up to 256 users in each group. Group or user numbering runs from 0 to 255. The naming of the groups and the users within the groups is arbitrary. Typically, users with similar job functions are placed in the same group, such as operations personnel, development personnel, or systems personnel. Once a group has been established, any new users that are added to the group must use the group name. Therefore, all users added to the group ACCT, or group number 140, must use the group name ACCT. The individual names within the group must be unique and must correspond to individual user numbers. Process Naming. All executing processes on a Tandem system are identified by the CPUs number in which they are running and by the process number that they began as in that CPUs. This is referred to as the PIN. The PIN is identified in the following format: <cpu number>,<process number>, or 0,15. Of and by themselves, PINs are not very descriptive; therefore, processes can also be started as named processes. Named processes are identified in the following format: $<process name>, or $ZSMP. Processes can also have subprocesses, which are identified as $<process name>.#<subprocess name>, or $S.#LPT. Device Naming. Devices are named in the SYStem GENeration configuration file. They are identified as $<device name>, or $TAPE. Devices can also have associated subdevices, which are named as $<device name>.#<subdevice name>, or $TAPE.#A01. Understanding Nonstop Guardian Security Tandem takes a three-tiered approach to security in its NonStop Guardian application: authentication, authorization, and auditing. Each of these tiers is discussed in the following sections. Authentication Authentication is the process in which users' requests for access are evaluated by the system. Tandem's screening process is based on a user hierarchy that groups users by job function and by the operations that the specific groups are authorized to perform. User Hierarchy. The Tandem user structure is hierarchical in design. The user ID 255,255is always placed at the top of the structure of any Tandem system. On most systems, this ID is called SUPER.SUPER. It is possible to change the name, but it is not possible to change the unique user ID of 255,255. Generically, this ID is referred to as the Super ID, and it is the ultimate ID on any Tandem system. Because it can perform any action on any object on the system, the Super ID is highly sensitive and its password must be protected. Group Managers form the next tier of the hierarchy. Group Managers have a subset of Previous screen the capabilities of the Super ID. Their range of influence is limited to the objects owned by users in their own groups. Within each group are the group members. Group members have the capability to perform many activities on the system, most of which are limited to objects owned by themselves.
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