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ITL Bulletin for February 2003
From: InfoSec News <isn () c4i org>
Date: Fri, 28 Feb 2003 00:54:54 -0600 (CST)

---------- Forwarded message ----------
Date: Thu, 27 Feb 2003 10:28:56 -0500 (EST)
From: Elizabeth Lennon <elizabeth.lennon () nist gov>
To: Multiple recipients of list <itl-bulletin () nist gov>
Subject: ITL Bulletin for February 2003

Shirley Radack, Editor
Computer Security Division
Information Technology Laboratory
National Institute of Standards and Technology

Organizations may decide to interconnect their information technology
(IT) systems so they can share their data and information resources
with each other. Benefits that participating organizations may realize
include reduced operating costs, greater functionality, improved
efficiency, and centralized access to data. Organizations choose to
interconnect their IT systems for a variety of reasons, depending on
their organizational needs or the requirements of Congressional
mandates or Executive department agreements.

National Institute of Standards and Technology (NIST)  Special
Publication (SP) 800-47, Security Guide for Interconnecting
Information Technology Systems, provides guidance for planning,
establishing, maintaining, and terminating secure yet cost-effective
interconnections between IT systems that are owned and operated by
different organizations. This ITL Bulletin summarizes the document,
which also discusses the benefits of interconnecting IT systems, the
basic components of an interconnection, the methods and levels of
interconnectivity, and the potential security risks associated with
interconnections. Written by Tim Grance, Joan Hash, Steven Peck,
Jonathan Smith, and Karen Korow-Diks, NIST SP 800-47 is available at

The appendices contain sample documents to help organizations
interconnect their IT systems, including an Interconnection Security
Agreement (ISA), which specifies the technical and security
requirements of the interconnection; a Memorandum of
Understanding/Agreement (MOU/A), which defines the responsibilities of
the participating organizations; and a System Interconnection
Implementation Plan, which defines the process for establishing the
interconnection. Also included are a glossary, references, and an

Interconnection Issues

Organizations deciding to interconnect their systems should determine
the method of interconnection. IT systems can be interconnected by a
dedicated line that either is owned by one of the organizations or is
leased from a third party, such as an Integrated Services Digital
Network (ISDN), a T1, or a T3 line. Dedicated physical lines provide a
higher level of security for the interconnected systems, because they
can be breached only through direct physical access to the line.
However, dedicated lines can be expensive.

A less expensive alternative to the dedicated line is interconnection
over a public network, using a virtual private network (VPN). A VPN is
a data network that enables two or more parties to communicate
securely across a public network by creating a private connection, or
"tunnel,"  between them. This alternative can be less secure than the
dedicated line, however, because unauthorized parties could intercept
unprotected data that is transmitted over the public network.

Interconnected IT systems can expose the participating organizations
to risks. In planning for interconnected systems, organizations should
apply risk management procedures. Federal agencies are required to
protect government information commensurate with the risk and
magnitude of harm that could result from the loss, misuse,
unauthorized access, or modification of such information.

If the interconnection is not properly designed, security failures
could compromise the connected systems and the data they store,
process, or transmit. In addition, if one of the connected systems is
compromised, the interconnection could be used to compromise the other
system and its data. In most cases, the participating organizations
have little or no control over the operation and management of the
other party's system.

Therefore, both parties should learn as much as possible about the
risks associated with the planned or current interconnection and the
security controls that they can implement to mitigate those risks. A
written agreement is needed to establish and describe the management,
operation, and use of the interconnection. The agreement should be
reviewed and approved by appropriate senior staff from each

OMB Circular A-130, Appendix III, requires agencies to obtain written
management authorization before connecting agency IT systems to other
systems, based on an acceptable level of risk. The written
authorization should define the rules of behavior and controls that
must be maintained for the system interconnection, and it should be
included in the agencies' system security plans.

Four Phases of the System Interconnection Life Cycle

The NIST SP 800-47 guide recommends a "life-cycle management" approach
for interconnecting IT systems:

( planning for the interconnection;
( establishing the interconnection;
( maintaining the interconnection; and
( disconnecting an interconnection.

Planning for the Interconnection.

The planning phase is the first step in establishing an efficient and
secure interconnection. The participating organizations should examine
all relevant technical, security, and administrative issues; and form
an agreement governing the management, operation, and use of the

A joint planning team should be established by the participating
organizations, composed of management and technical staff, including
program managers, security officers, system administrators, network
administrators, and system architects. The joint planning team should
coordinate the planning process with the support of senior managers
and system and data owners. The team would be responsible for
coordinating all aspects of the planning process and ensuring that it
had clear direction and sufficient resources. After the initial
planning phase, the team may remain active to discuss future issues
involving the interconnection.

         The business case for the interconnection should be defined,
including its purpose and expected benefits, costs for staff and
equipment, and potential technical, legal, and financial risks.
Privacy issues and access rules also should be discussed.

         Systems to be interconnected should be certified and
accredited in accordance with federal certification and accreditation
(C&A) guidelines. Certification involves testing and evaluating the
technical and nontechnical security features of the system to
determine the extent to which it meets a set of specified security
requirements.  Accreditation is the official approval by a Designated
Approving Authority (DAA) or other authorizing management official
that the system may operate for a specific purpose using a defined set
of safeguards at an acceptable level of risk.

         The planning team should consider the interconnection
requirements, including all relevant technical, security,
administrative, and personnel issues.  This information will be used
to develop an Interconnection Security Agreement (ISA) and a
Memorandum of Understanding or Agreement (MOU/A). Further, the
collected information may be used to develop an implementation plan
for establishing the interconnection. Issues that should be considered
include the level and method of the interconnection, impact on
existing operations, hardware and software requirements, data
sensitivity, user community, security controls, and rules of behavior,
among others.

         The joint planning team should document an agreement
governing the interconnection and the terms under which the
organizations will abide by the agreement, based on the team's review
of all relevant technical, security, administrative, and personnel
issues. An ISA should be developed to specify the technical and
security requirements for establishing, operating, and maintaining the
interconnection. The MOU/A documents the terms and conditions for
sharing data and information resources in a secure manner.

         The ISA and MOU/A should be reviewed by management officials
of participating organizations and approved or rejected. Approval of
the ISA and MOU/A constitutes approval of the interconnection.
Approval may also be granted on an interim basis. The ISA and MOU/A
that are developed should be kept in a secure location to protect
against theft, damage, or destruction. Copies stored electronically
should be protected from unauthorized disclosure or modification.

Establishing an Interconnection.

The following steps are recommended for establishing a system
interconnection after it has been planned and approved. The
participating organizations develop and execute a plan for the
interconnection, including security controls.

The joint planning team should develop an implementation plan. The
plan should document all aspects of the interconnection effort and
clarify how technical requirements specified in the ISA will be
implemented. The plan should include a description of the IT systems
to be interconnected, the sensitivity of the data to be exchanged, the
staff members who will be responsible for the interconnected systems,
and the security controls, tests, and procedures that will be in

The implementation plan should be reviewed and approved by the
planning team. Once approved, the plan may be implemented. Recommended
steps for establishing the interconnection are described below.

Security controls should be implemented or configured.  These controls
may include firewalls and intrusion detection systems. Audit logs
should be installed to record the activities that take place across
the interconnection and should be appropriately reviewed, protected,
and maintained. Identification and authentication procedures should be
established to prevent unauthorized access to the interconnected
systems. Passwords, biometrics, and smart cards are additional
measures that may be used.

Logical access controls should be used to designate users who have
access to system resources and the type of transactions and functions
that they are permitted to perform. Data passing from one system to
another should be scanned with antivirus software to detect and
eliminate malicious code. Antivirus software should be installed on
all servers and computer workstations linked to the interconnection.
The software should be automatically updated and maintained with
current virus definitions.

Encryption can be used to protect the confidentiality and integrity of
data during transmission and storage, to authenticate users to the
interconnection and to shared applications, and to provide for
nonrepudiation of data.

Hardware and software supporting the interconnection should be located
in a secure location that is protected from unauthorized access,
interference, or damage.  Interconnections should be protected from
hazards such as fire, water, and excessive heat and humidity. Computer
workstations should be in secure areas to protect them from damage,
loss, theft, or unauthorized physical access.

Hardware and software to establish the interconnection should be
installed or configured. The hardware and software should be installed
with proper communications lines, VPN software, routers, and switches.
Database, web, and application servers should support services
provided across the interconnection, and needed hubs should be
installed to join multiple computers into a single network segment.
Computer workstations should be configured to provide authorized users
with a link to the interconnection.

Applications or protocols for services that are provided across the
interconnection should be integrated. These includes word processing,
database applications, e-mail, web browsers, application servers,
authentication servers, domain servers, development tools, editing
programs, and communications programs.

Conduct operational and security testing to ensure equipment operates
properly and to mitigate or counter the ways for unauthorized users to
circumvent or defeat security controls. The interface between
applications should be tested across the interconnection, and security
controls should be tested under realistic conditions.  Testing should
be done in an isolated, non-operational environment to avoid
disturbing the systems. Weaknesses or problems should be corrected,
and the interconnection retested. Operational and security testing may
be performed as part of the recertification and reaccreditation

Conduct security training and awareness for all authorized personnel
who will be involved in managing, using, and/or operating the
interconnection. Ensure that staff members understand the rules and
that they know how to report suspicious or prohibited activities.

Both organizations should update their system security plans and
related documents to reflect the changed security environment in which
their respective systems operate. The MOU/A should address the details
of conducting a mutual review of the interconnection.

Perform recertification and reaccreditation if significant changes
have been made to the connected systems.

Activate the interconnection for use by both organizations.  One or
both organizations should monitor the interconnection for at least
three months to ensure that it operates properly and securely.

Maintaining the Interconnection.

After it is established, the interconnection must be actively
maintained for secure operation. The maintenance steps are:

         Maintain clear lines of communication to ensure that the
interconnection is properly maintained and that both sides are
notified of changes or security incidents.  Communications should be
conducted between designated personnel using approved procedures.

Authorized personnel should maintain the equipment in accordance with
the manufacturer's specifications.  Appropriate documentation and
notification procedures should be used.

User profiles should be managed to assure access to authorized users
only.  Active management of user profiles helps to prevent intruders
from using inactive accounts.

Security reviews should be conducted to ensure security controls are
working properly and providing appropriate levels of protection.

Audit logs should be analyzed at predetermined intervals to detect and
track unusual or suspicious activities across the interconnection that
might indicate intrusions or internal misuse.

Security incidents should be reported to participating organizations.
Both organizations should respond to security incidents by isolating
systems if necessary and by coordinating their incident response

Coordinate contingency planning, training, testing, and exercises to
minimize the impact of disasters and other contingencies that could
damage the connected systems or jeopardize the confidentiality and
integrity of shared data.

Perform change management procedures to ensure that the
interconnection is properly maintained and secured. A change control
board should review and approve planned changes for each organization.
Changes should be based on the security requirements specified in the
ISA and a determination that the change will not adversely affect the
interconnection. A joint change control board should review and
approve changes that affect the interconnection.

Update system security plans and other relevant documentation at least
annually or whenever there is a significant change to the IT systems
or to the interconnection.

Disconnecting an Interconnection.

If an interconnection must be terminated, the process should be
conducted in a methodical manner to avoid disrupting the IT system of
either organization. The decision to terminate the interconnection
should be made by the system owner with the advice of appropriate
managerial and technical staff. Before terminating the
interconnection, the initiating party should notify the other party in
writing, and it should receive an acknowledgment in return.

If an organization detects an attack, intrusion attempt, or other
contingency that exploits or jeopardizes the connected systems or
data, it may be necessary to abruptly terminate the interconnection
without written notice to the other party. This is an extraordinary
measure taken only in extreme circumstances and only after
consultation with appropriate technical staff and senior management.

Both organizations may choose to restore the system interconnection
after it has been terminated. The decision to restore the
interconnection should be based on the cause and duration of the
disconnection. Both organizations should modify the ISA and MOU/A to
address issues requiring attention. If the interconnection has been
terminated for more than 90 days, each party should perform a risk
assessment on its respective system and reexamine all relevant
planning and implementation issues, including developing a new ISA and


Interconnecting IT systems can provide significant benefits to
participating organizations, but can expose both to risks.
Interconnections must be properly designed, and appropriate security
controls must be in place to avoid compromise of systems and data.
Both parties must understand the risks associated with the
interconnection and the security controls they can implement to
mitigate those risks. The organizations should establish a formal
agreement concerning the management, operation, and use of the
interconnection. The agreement should be reviewed and approved by
appropriate senior staff from each organization.

Reference List

NIST's Information Technology Laboratory issues publications covering
research, guidance, standards, and the results of collaborative
outreach efforts with industry, government, and academic
organizations. NIST publications dealing with information security
topics, including archived copies of bulletins, are available in
electronic format from the NIST Computer Security Resource Center at
http://csrc.nist.gov/publications/ .

The following NIST Special Publications provide guidance to help
organizations plan, establish, maintain, and terminate secure IT
system interconnections:

NIST Special Publication 800-3, Establishing a Computer Security
Incidence Response Capability (CSIRC), provides information on
detecting and reporting security incidents.

NIST Special Publication 800-12, An Introduction to Computer Security:
The NIST Handbook, provides guidance on certification and
accreditation (C&A), and other security procedures.

NIST Special Publication 800-18, Guide for Developing Security Plans
for Information Technology Systems, provides details on access control
issues, and developing and updating security plans.

NIST Special Publication 800-30, Risk Management Guide for Information
Technology Systems, provides guidance on conducting risk assessments.

NIST Special Publication 800-31, Intrusion Detection Systems (IDS),
and NIST Special Publication 800-41, Guidelines on Firewalls and
Firewall Policy, provide information on selection of security

NIST Special Publication 800-34, Contingency Planning Guide for
Information Technology Systems, gives information on coordinating
contingency planning activities.

Guidance on physical security techniques is included in NIST Special
Publications 800-12, An Introduction to Computer Security: The NIST
Handbook; NIST Special Publication 800-27, Engineering Principles for
Information Technology Security (A Baseline for Achieving Security);  
and NIST Special Publication 800-30, Risk Management Guide for
Information Technology Systems.

Details on integrating applications and protocols can be found in NIST
Special Publication 800-27, Engineering Principles for Information
Technology Security (A Baseline for Achieving Security); NIST Special
Publication 800-28, Guidelines on Active Content and Mobile Code; and
NIST Special Publication 800-33, Underlying Technical Models for
Information Technology Security.

NIST Special Publication 800-42 (draft), Guidelines on Network
Security Testing, includes a methodology for using network-based tools
to test IT systems for vulnerabilities.

Information about Federal Information Processing Standards
(FIPS)-approved algorithms and cryptographic modules that must be used
by federal agencies is available at


Any mention of commercial products or reference to commercial
organizations is for information only; it does not imply
recommendation or endorsement by NIST nor does it imply that the
products mentioned are necessarily the best available for the purpose.

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