Special Publication 800-12: An Introduction to Computer Security - The NIST Handbook
|System management and administration staff generally perform support and operations tasks although sometimes users do. Larger systems may have full-time operators, system programmers, and support staff performing these tasks. Smaller systems may have a part-time administrator.|
Computer support and operations refers to everything done to run a computer system. This includes both system administration and tasks external to the system that support its operation (e.g., maintaining documentation). It does not include system planning or design. The support and operation of any computer system, from a three-person local area network to a worldwide application serving thousands of users, is critical to maintaining the security of a system. Support and operations are routine activities that enable computer systems to function correctly. These include fixing software or hardware problems, loading and maintaining software, and helping users resolve problems.
The failure to consider security as part of the support and operations of computer systems is, for many organizations, their Achilles heel. Computer security system literature includes many examples of how organizations undermined their often expensive security measures because of poor documentation, old user accounts, conflicting software, or poor control of maintenance accounts. Also, an organization's policies and procedures often fail to address many of these important issues.
The important security considerations within some of the major categories of support and operations are:
|The primary goal of computer support and operations is the continued and correct operation of a computer system. One of the goals of computer security is the availability and integrity of systems. These goals are very closely linked.|
Some special considerations are noted for larger or smaller systems.101
This chapter addresses the support and operations activities directly related to security. Every control discussed in this handbook relies, in one way or another, on computer system support and operations. This chapter, however, focuses on areas not covered in other chapters. For example, operations personnel normally create user accounts on the system. This topic is covered in the Identification and Authentication chapter, so it is not discussed here. Similarly, the input from support and operations staff to the security awareness and training program is covered in the Security Awareness, Training, and Education chapter.
In many organizations, user support takes place through a Help Desk. Help Desks can support an entire organization, a subunit, a specific system, or a combination of these. For smaller systems, the system administrator normally provides direct user support. Experienced users provide informal user support on most systems.
|User support should be closely linked to the organization's incident handling capability. In many cases, the same personnel perform these functions.|
An important security consideration for user support personnel is being able to recognize which problems (brought to their attention by users) are security-related. For example, users' inability to log onto a computer system may result from the disabling of their accounts due to too many failed access attempts. This could indicate the presence of hackers trying to guess users' passwords.
In general, system support and operations staff need to be able to identify security problems, respond appropriately, and inform appropriate individuals. A wide range of possible security problems exist. Some will be internal to custom applications, while others apply to off-the-shelf products. Additionally, problems can be software- or hardware-based.
|Small systems are especially susceptible to viruses, while networks are particularly susceptible to hacker attacks, which can be targeted at multiple systems. System support personnel should be able to recognize attacks and know how to respond.|
The more responsive and knowledgeable system support and operation staff personnel are, the less user support will be provided informally. The support other users provide is important, but they may not be aware of the "whole picture."
Software is the heart of an organization's computer operations, whatever the size and complexity of the system. Therefore, it is essential that software function correctly and be protected from corruption. There are many elements of software support.
One is controlling what software is used on a system. If users or systems personnel can load and execute any software on a system, the system is more vulnerable to viruses, to unexpected software interactions, and to software that may subvert or bypass security controls. One method of controlling software is to inspect or test software before it is loaded (e.g., to determine compatibility with custom applications or identify other unforeseen interactions). This can apply to new software packages, to upgrades, to off-the-shelf products, or to custom software, as deemed appropriate. In addition to controlling the loading and execution of new software, organizations should also give care to the configuration and use of powerful system utilities. System utilities can compromise the integrity of operating systems and logical access controls.
take advantage of the weak software controls in personal computers.
Also, there are powerful utilities available for PCs that can
restore deleted files, find hidden files, and interface directly
with PC hardware, bypassing the operating system. Some organizations
use personal computers without floppy drives in order to have
better control over the system.
are several widely available utilities that look for security
problems in both networks and the systems attached to them.
Some utilities look for and try to exploit security vulnerabilities.
(This type of software is further discussed in Chapter 9.)
A second element in software support can be to ensure that software has not been modified without proper authorization. This involves the protection of software and backup copies. This can be done with a combination of logical and physical access controls.
Many organizations also include a program to ensure that software is properly licensed, as required. For example, an organization may audit systems for illegal copies of copyrighted software. This problem is primarily associated with PCs and LANs, but can apply to any type of system.
Closely related to software support is configuration management -- the process of keeping track of changes to the system and, if needed, approving them.2 Configuration management normally addresses hardware, software, networking, and other changes; it can be formal or informal. The primary security goal of configuration management is ensuring that changes to the system do not unintentionally or unknowingly diminish security. Some of the methods discussed under software support, such as inspecting and testing software changes, can be used. Chapter 9 discusses other methods.
|For networked systems, configuration management should include external connections. Is the computer system connected? To what other systems? In turn, to what systems are these systems and organizations connected?|
Note that the security goal is to know what changes occur, not to prevent security from being changed. There may be circumstances when security will be reduced. However, the decrease in security should be the result of a decision based on all appropriate factors.
A second security goal of configuration management is ensuring that changes to the system are reflected in other documentation, such as the contingency plan. If the change is major, it may be necessary to reanalyze some or all of the security of the system. This is discussed in Chapter 8.
|Users of smaller systems are often responsible for their own backups. However, in reality they do not always perform backups regularly. Some organizations, therefore, task support personnel with making backups periodically for smaller systems, either automatically (through server software) or manually (by visiting each machine).|
Support and operations personnel and sometimes users back up software and data. This function is critical to contingency planning. Frequency of backups will depend upon how often data changes and how important those changes are. Program managers should be consulted to determine what backup schedule is appropriate. Also, as a safety measure, it is useful to test that backup copies are actually usable. Finally, backups should be stored securely, as appropriate (discussed below).
Media controls include a variety of measures to provide physical and environmental protection and accountability for tapes, diskettes, printouts, and other media. From a security perspective, media controls should be designed to prevent the loss of confidentiality, integrity, or availability of information, including data or software, when stored outside the system. This can include storage of information before it is input to the system and after it is output.
The extent of media control
depends upon many factors, including the type of data, the quantity
of media, and the nature of the user environment. Physical and environmental
protection is used to prevent unauthorized individuals from accessing
the media. It also protects against such factors as heat, cold,
or harmful magnetic fields. When necessary, logging the use of individual
media (e.g., a tape cartridge) provides detailed accountability
-- to hold authorized people responsible for their actions.
Controlling media may require some form of physical labeling. The labels can be used to identify media with special handling instructions, to locate needed information, or to log media (e.g., with serial/control numbers or bar codes) to support accountability. Identification is often by colored labels on diskettes or tapes or banner pages on printouts.
|Typical markings for media could include: Privacy Act Information, Company Proprietary, or Joe's Backup Tape. In each case, the individuals handling the media must know the applicable handling instructions. For example, at the Acme Patent Research Firm, proprietary information may not leave the building except under the care of a security officer. Also, Joe's Backup Tape should be easy to find in case something happens to Joe's system.|
If labeling is used for special handling instructions, it is critical that people be appropriately trained. The marking of PC input and output is generally the responsibility of the user, not the system support staff. Marking backup diskettes can help prevent them from being accidentally overwritten.
The logging of media is used to support accountability. Logs can include control numbers (or other tracking data), the times and dates of transfers, names and signatures of individuals involved, and other relevant information. Periodic spot checks or audits may be conducted to determine that no controlled items have been lost and that all are in the custody of individuals named in control logs. Automated media tracking systems may be helpful for maintaining inventories of tape and disk libraries.
When electronically stored information is read into a computer system, it may be necessary to determine whether it has been read correctly or subject to any modification. The integrity of electronic information can be verified using error detection and correction or, if intentional modifications are a threat, cryptographic-based technologies. (See Chapter 19.)
Media can be stolen, destroyed, replaced with a look-alike copy, or lost. Physical access controls, which can limit these problems, include locked doors, desks, file cabinets, or safes.
If the media requires protection at all times, it may be necessary to actually output data to the media in a secure location (e.g., printing to a printer in a locked room instead of to a general-purpose printer in a common area).
Physical protection of
media should be extended to backup copies stored offsite. They generally
should be accorded an equivalent level of protection to media containing
the same information stored onsite. (Equivalent protection does
not mean that the security measures need to be exactly the same.
The controls at the off-site location are quite likely to be different
from the controls at the regular site.) Physical access is discussed
in Chapter 15.
Magnetic media, such as diskettes or magnetic tape, require environmental protection, since they are sensitive to temperature, liquids, magnetism, smoke, and dust. Other media (e.g., paper and optical storage) may have different sensitivities to environmental factors.
Media control may be transferred both within the organization and to outside elements. Possibilities for securing such transmittal include sealed and marked envelopes, authorized messenger or courier, or U.S. certified or registered mail.
|Many people throw away old diskettes, believing that erasing the files on the diskette has made the data un-retrievable. In reality, however, erasing a file simply removes the pointer to that file. The pointer tells the computer where the file is physically stored. Without this pointer, the files will not appear on a directory listing. This does not mean that the file was removed. Commonly available utility programs can often retrieve information that is presumed deleted.|
When media is disposed of, it may be important to ensure that information is not improperly disclosed. This applies both to media that is external to a computer system (such as a diskette) and to media inside a computer system, such as a hard disk. The process of removing information from media is called sanitization.
Three techniques are commonly used for media sanitization: overwriting, degaussing, and destruction. Overwriting is an effective method for clearing data from magnetic media. As the name implies, overwriting uses a program to write (1s, 0s, or a combination) onto the media. Common practice is to overwrite the media three times. Overwriting should not be confused with merely deleting the pointer to a file (which typically happens when a delete command is used). Overwriting requires that the media be in working order. Degaussing is a method to magnetically erase data from magnetic media. Two types of degausser exist: strong permanent magnets and electric degaussers. The final method of sanitization is destruction of the media by shredding or burning.
Documentation of all aspects of computer support and operations is important to ensure continuity and consistency. Formalizing operational practices and procedures with sufficient detail helps to eliminate security lapses and oversights, gives new personnel sufficiently detailed instructions, and provides a quality assurance function to help ensure that operations will be performed correctly and efficiently.
The security of a system also needs to be documented. This includes many types of documentation, such as security plans, contingency plans, risk analyses, and security policies and procedures. Much of this information, particularly risk and threat analyses, has to be protected against unauthorized disclosure. Security documentation also needs to be both current and accessible. Accessibility should take special factors into account (such as the need to find the contingency plan during a disaster).
should be designed to fulfill the needs of the different types of
people who use it. For this reason, many organizations separate
documentation into policy and procedures. A security
procedures manual should be written to inform various system
users how to do their jobs securely. A security procedures manual
for systems operations and support staff may address a wide variety
of technical and operational concerns in considerable detail.
System maintenance requires either physical or logical access to the system. Support and operations staff, hardware or software vendors, or third-party service providers may maintain a system. Maintenance may be performed on site, or it may be necessary to move equipment to a repair site. Maintenance may also be performed remotely via communications connections. If someone who does not normally have access to the system performs maintenance, then a security vulnerability is introduced.
In some circumstances,
it may be necessary to take additional precautions, such as conducting
background investigations of service personnel. Supervision of maintenance
personnel may prevent some problems, such as "snooping around"
the physical area. However, once someone has access to the system,
it is very difficult for supervision to prevent damage done through
the maintenance process.
|One of the most common methods hackers use to break into systems is through maintenance accounts that still have factory-set or easily guessed passwords.|
Many computer systems provide maintenance accounts. These special log-in accounts are normally preconfigured at the factory with pre-set, widely known passwords. It is critical to change these passwords or otherwise disable the accounts until they are needed. Procedures should be developed to ensure that only authorized maintenance personnel can use these accounts. If the account is to be used remotely, authentication of the maintenance provider can be performed using call-back confirmation. This helps ensure that remote diagnostic activities actually originate from an established phone number at the vendor's site. Other techniques can also help, including encryption and decryption of diagnostic communications; strong identification and authentication techniques, such as tokens; and remote disconnect verification.
Larger systems may have diagnostic ports. In addition, manufacturers of larger systems and third-party providers may offer more diagnostic and support services. It is critical to ensure that these ports are only used by authorized personnel and cannot be accessed by hackers.
There are support and operations components in most of the controls discussed in this handbook.
Personnel. Most support and operations staff have special access to the system. Some organizations conduct background checks on individuals filling these positions to screen out possibly untrustworthy individuals.
Incident Handling. Support and operations may include an organization's incident handling staff. Even if they are separate organizations, they need to work together to recognize and respond to incidents.
Contingency Planning. Support and operations normally provides technical input to contingency planning and carries out the activities of making backups, updating documentation, and practicing responding to contingencies.
Security Awareness, Training, and Education. Support and operations staff should be trained in security procedures and should be aware of the importance of security. In addition, they provide technical expertise needed to teach users how to secure their systems.
Physical and Environmental. Support and operations staff often controls the immediate physical area around the computer system.
Technical Controls. The technical controls are installed, maintained, and used by support and operations staff. They create the user accounts, add users to access control lists, review audit logs for unusual activity, control bulk encryption over telecommunications links, and perform the countless operational tasks needed to use technical controls effectively. In addition, support and operations staff provides needed input to the selection of controls based on their knowledge of system capabilities and operational constraints.
Assurance. Support and operations staff ensures that changes to a system do not introduce security vulnerabilities by using assurance methods to evaluate or test the changes and their effect on the system. Operational assurance is normally performed by support and operations staff.
The cost of ensuring adequate security in day-to-day support and operations is largely dependent upon the size and characteristics of the operating environment and the nature of the processing being performed. If sufficient support personnel are already available, it is important that they be trained in the security aspects of their assigned jobs; it is usually not necessary to hire additional support and operations security specialists. Training, both initial and ongoing, is a cost of successfully incorporating security measures into support and operations activities.
Another cost is that associated with creating and updating documentation to ensure that security concerns are appropriately reflected in support and operations policies, procedures, and duties.
Bicknell, Paul. "Data Security for Personal Computers." Proceedings of the 15th National Computer Security Conference. Vol. I. National Institute of Standards and Technology and National Computer Security Center. Baltimore, MD. October 1992.
Caelli, William, Dennis Longley, and Michael Shain. Information Security Handbook. New York, NY: Stockton Press, 1991.
Carnahan, Lisa J. "A Local Area Network Security Architecture." Proceedings of the 15th National Computer Security Conference. Vol. I. National Institute of Standards and Technology and National Computer Security Center. Baltimore, MD. 1992.
Carroll, J.M. Managing Risk: A Computer-Aided Strategy. Boston, MA: Butterworths, 1984.
Chapman, D. Brent. "Network (In)Security Through IP Packet Filtering." Proceedings of the 3rd USENIX UNIX Security Symposium, 1992.
Curry, David A. UNIX System Security: A Guide for Users and System Administrators. Reading, MA: Addison-Wesley Publishing Co., Inc., 1992.
Garfinkel, Simson, and Gene Spafford. Practical UNIX Security. Sebastopol, CA: O'Reilly & Associates, 1991.
Holbrook, Paul, and Joyce Reynolds, eds. Site Security Handbook. Available by anonymous ftp from nic.ddn.mil (in rfc directory).
Internet Security for System & Network Administrators. Computer Emergency Response Team Security Seminars, CERT Coordination Center, 1993.
Murray, W.H. "Security Considerations for Personal Computers." Tutorial: Computer and Network Security. Oakland, CA: IEEE Computer Society Press, 1986.
Parker, Donna B. Managers Guide to Computer Security. Reston, VA: Reston Publishing, Inc., 1981.
Pfleeger, Charles P. Security in Computing. Englewood Cliffs, NJ: Prentice-Hall, Inc., 1989.
In general, larger systems include mainframes, large minicomputers,
and WANs. Smaller systems include PCs and LANs.
102. This chapter only addresses configuration management during the operational phase. Configuration management can have extremely important security consequences during the development phase of a system.
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July 6, 2007
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