Tài liệu Basic Security Policy pdf

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Basic Security Policy

Version 1.7 - July 5, 2001


I keep six honest serving men
(They taught me all I knew);
Their names are What and Why and When
And How and Where and Who.
--Rudyard Kipling





CONTRIBUTING AUTHORS:

Doug Austin Dyncorp Information Systems, LLC
Alexander Bryce Alexander, Ltd.
Rob Dinehart IBJ Whitelhall Financial Group
Brian M. Estep Adelphia Business Solutions
Robert Ishimoto Robert Ishimoto Consulting
Stephen Joyce bitLab, LLC
Carol Kramer SANS Institute
Randy Marchany Virginia Tech Computing Center
Stephen Northcutt SANS Institute

John Ritter Intecs International, Inc.
Matt Scarborough IC
Arrigo Triulzi Albourne Parners, Ltd.

EDITED BY: Carol Kramer, Stephen Northcutt, Fred Kerby

If you have corrections or additions or would like to be involved in
enhancing this project, please send email to:

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A note from Stephen Northcutt:

I never cease to be amazed by the fact that you can’t take a class in Information Security without
being told to do this or that in accordance with “your security policy”, but nobody ever explains
what the policy is let alone how to write or evaluate it.

That is why we undertook this research and education project into basic security policy. We
hope you will find this module useful and that you will participate in its evolution. Consensus is
a powerful tool. We need the ideas and criticisms from the information security community in
order to make this The Roadmap for usable, effective policy.

Thank you!



Stephen Northcutt


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CONTENTS

1. PREFACE

2. DEFINING SECURITY POLICY

3. USING SECURITY POLICY TO MANAGE RISK

4. IDENTIFYING SECURITY POLICY

5. SECURITY POLICY WORKSHEET

6. EVALUATING SECURITY POLICY

7. ISSUE-SPECIFIC SECURITY POLICY

7.1 Anti-Virus

7.2 Password Assessment

7.3 Backups

7.4 Incident Handling

7.5 Proprietary Information

7.6 Personal Data Assistants

8. WRITING A PERSONAL SECURITY POLICY

9. EXERCISES

APPENDIX A - Policy Templates

APPENDIX B - Sample Non-Disclosure Agreement

APPENDIX C – References
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1. PREFACE

S
ecurity policy protects both people and information.

Safeguarding information is challenging when records are created and stored on
computers. We live in a world where computers are globally linked and accessible,
making digitized information especially vulnerable to theft, manipulation, and
destruction. Security breaches are inevitable. Crucial decisions and defensive action
must be prompt and precise.

A security policy establishes what must be done to protect information stored on
computers. A well-written policy contains sufficient definition of “what” to do so that
the “how” can be identified and measured or evaluated.

An effective security policy also protects people. Anyone who makes decisions or takes
action in a situation where information is at risk incurs personal risk as well. A security
policy allows people to take necessary actions without fear of reprisal. Security policy
compels the safeguarding of information, while it eliminates, or at least reduces,
personal liability for employees.

Please take a minute and turn to the back of this book and examine the non-disclosure

agreement in Appendix A.

This is one of two examples in the book that is not written in plain English. This legal
document is based on the actual non-disclosure agreement that GIAC uses when
disclosing proprietary information. Despite the lawyer language of the document, it
doesn’t take long to see that the purpose of this is to protect information. It carefully
spells out the procedures, the who, what, where, when and how for the case where an
organization has sensitive information that it is going to disclose to an individual. As
we learn more about policies, we will find that many aspects of a policy can be found in
a document like this. In fact, an organization’s policy might reference a document like
this. For instance, an organization may have a policy that says, "sensitive information
shall only be released to individuals who have signed a non-disclosure agreement that
is on file with the corporate legal office". Now that we have an example of a policy that
protects information, I would like to show an example of a policy that protected an
individual - in this case, me.


Sinking a Warship
I was scanning our entire Navy lab, one subnet at a time (the recommended approach),
fixing problems as I found them. I was running the scanner on low power when I hit a network
and received a phone call from a friend. "Stephen, the net is down, we think you killed it".
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"It" was a mock up of a real Navy warship. All of the communications on the model were
the same as the one on the real ship. When its networking hardware received a packet (from me)
on a certain port, it died. Its FDDI ring came to a complete stop.
The people in this little lab were furious with me. They formed an investigative panel and
called me in. I could see by the grim looks all around the table that this was not going to be
pleasant. The sparks flew; one fellow in particular wanted to do me harm. He continues to be
angry with me to this day! Finally someone asked whether could happen in real life. The answer
was “yes”. The next question was, “then shouldn’t we get it fixed”?

The point is, my network scan made these people angry enough that my job would have
been in jeopardy if I’d not had my ducks in a row. I’d received permission to run the scan prior
to doing so. So should you!
Stephen Northcutt


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2. DEFINING SECURITY POLICY

A policy is a guideline or directive which indicates a conscious decision to follow a path towards
an objective defined in the policy. Often a policy may institute, empower resources, or direct
action by providing procedures or actions to be carried out. With that in mind, this course will
attempt to provide guidance towards the goal of developing a Basic Security Policy for an
organization, or better defining the existing one. The policy itself should be both effective and
realistic with achievable security goals.

Without a security policy, any organization can be left exposed to the world. In order to
determine your policy needs, a risk assessment must first be conducted. This may require an
organization to define levels of sensitivity with regard to information, processes, procedures, and
systems.

The security policy should seek a balance between “Access” and “Security”. Of these two points
“Access” pertains to performance and ease of use, while “Security” focuses on integrity,
availability, and safety. This does not just apply to the computer or network itself, but to the
organization as a whole.

During this presentation three references to policy types will be made. It may be inferred that the
policy being described when not specified is that of a program policy. Issue-specific polices will
be covered as well, while mentioning of system-specific policies may be brought out as well.
Let’s define these policy types before we get started:

Program Policy: This high-level policy sets the overall tone of an organization’s security
approach. Typically guidance is provided with this policy to enact the other types of policies and
who is responsible. This policy may provide direction for compliance with industry standards
such as ISO, QS, BS, AS, etc.
Issue-Specific Policy: These policies are intended to address specific needs within an
organization. This may include password procedures, Internet usage guidelines, etc,. This is not
as broad a policy category as the program policy; however, it is broader than the system-specific
policy.
System-Specific Policy: For a given organization there may be several systems that perform
various functions, where the use of one policy governing all of them may not be appropriate. It
may be necessary to develop a policy directed toward each system individually. This is a system-
specific policy.

A good security policy will take into account risks, vulnerabilities, and provide comprehensive
coverage of an organization’s infrastructure. Various security standards have been developed
over the years (C2, BS 7799, ISO 17799) which may or may not be applicable to a given
organization. While standards can provide an excellent point of departure for defining your
organization’s policy, if a policy does not directly relate to an organization’s realistic needs and
requirements the policy will fail at the risk of exposing the organization as though a policy were
absent. Security Policy should always be commensurate with actual measured risks.

Policy definition in the realm of security for the Internet Age has gained importance on
the world stage. The United Kingdom took a lead in the development of recognized
security standards and through the British Standards Institute sponsored the creation of
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the British Standard Code of Practice for Information Security Management (BS 7799).
The intention was to provide a means for ensuring customers that business were
providing secure services and that information was handled in a secure manner. This
standard was published in December 1, 2000 as an international standard (ISO/IEC
17799).

ISO/IEC 17799 provides well over 125 security guidelines that are divided into 10 major
headings. These headings enable identification of security controls in a manner, which
will be appropriate for a given organization. ISO/IEC 17799 provides security controls
for computers and networks, as well as guidance on security policies, staff security
awareness, business continuity planning, and legal requirements. In all, nearly 500
controls and elements of best practice are presented in ISO/IEC 17799.

As with any standard recognition, auditing teams and assessments are required to
determine eligibility for registration. ISO/IEC 17799 is a defining standard of security
controls that should be investigated and reviewed thoroughly before incorporation into
a business plan or operating procedure.

Each organization may work differently as it relates to policies and how they are
developed. The process of defining “policy” can be approached in much the same
format as defining an actual policy.

PROBLEM:
All security and technical classes talk about the necessity of basing
procedures on a good security policy. We need to understand what is meant by policy;
there are many conflicting definitions.

ACTION: Identify how your organization defines policy.

Step 1: Get a copy of your organization’s Policy Development Guide.
Ideally, the guide will describe what topics to include in the policy document. Typical
sections can include:
Purpose -
the reason for the policy.
Related documents – lists any documents (or other policy) that affect the contents

of this policy.
Cancellation
- identifies any existing policy that is cancelled when this policy
becomes effective.
Background -
provides amplifying information on the need for the policy.

Scope - states the range of coverage for the policy (to whom or what does the
policy apply?).
Policy statement
- identifies the actual guiding principles or what is to be done.
The statements are designed to influence and determine decisions and actions within
the scope of coverage. The statements should be prudent, expedient, and/or
advantageous to the organization.
Action - specifies what actions are necessary and when they are to be
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accomplished.
Responsibility
- states who is responsible for what. Subsections might identify
who will develop additional detailed guidance and when the policy will be reviewed
and updated.

Step 2: Determine who can sign the policy.
If you are part of a Department of Defense organization, the authority may be reserved
for the senior military officer. In other cases, it may be a senior vice president or a CIO
or other manager. In any case, the policy must be signed by someone with sufficient
authority and credibility that it is accepted by members of the organization to which it
applies.

Step 3: Identify the process used to get policy drafted, signed, and

implemented in your organization.
Once you’ve identified what should be in the policy and who will sign it, you need to
identify the folks who will help develop and review the policy before you submit it for
signature. Typical participants (in addition to the security staff) can include members
of the legal and human resources staff, as well as a representative from one or more
collective bargaining units.

Coaching Football
Think of a football game. Picture the coach at practice sessions, in the
locker room before the game. What is the coach doing? He is presenting, refining and
reworking a plan for winning the game, a plan that’s practiced over and over until it’s
perfect! We can see team captains and players referring to the plan before each play.
What does a game plan have to do with a computer security policy? The game plan is
actually a policy on how to win the game. The team that identifies its capabilities and
limitations, along with the capabilities and limitations of its opponents, will devise the
best plan and the best chance of winning if they follow it.

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3. USING SECURITY POLICY TO MANAGE RISK

PROBLEM: The only secure computer is one that is not connected to a network and is
powered off. Use of computers to process information has associated risks. You need a
methodology to validate that the organization is responsible and accountable for
managing that risk.

ACTION:
Learn how to manage risks related to your job.

Step 1: Identify risks.
Determine how your organization uses computers and networks in the conduct of

business, both routinely and under emergency circumstances. This will provide insight
into the risks that you face. Examples of some things that can pose risks include: using
the Internet, not using anti-virus software on desktop computers, permitting
customers/suppliers/partners to bypass the protection afforded by your firewall,
permitting personal use of corporate computers and networks.

Step 2: Communicate your findings.
Identifying risks is necessary, but not sufficient. Decision-makers need to know what
the risks are, as well as options for managing those risks. Be sure you have adequately
communicated the situation in writing to folks who can make a difference.

Step 3: Update the security policy as needed.
If there is no written policy in place, write it and get it signed by upper level
management. A well-written policy, signed by top executives, will identify the
corporation’s values and demonstrate that senior management supports the
information security activities required by the policy
.


Step 4: Develop and refine methods to measure compliance with the policy.
If you cannot measure compliance (conformance), the policy is unenforceable.

Where is it written…?
The decisions we make must stand the test of reasonableness: given the situation, could a
reasonable person be expected to make the same decision? It’s amazing to hear people who have
been practicing computer security for more than a decade, ask, “What instruction requires that
we do it that way? (or at all)". Having a written and dated policy signed by upper management
can help move these folks to where they need to be.

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4. IDENTIFYING SECURITY POLICY

PROBLEM: My organization doesn’t seem to have a security policy.

ACTION:
Identify what your organization does have, and try to make it better.
Your actions may include lobbying to create or expand current policy.

Step 1: Recognize that a policy can exist on different levels.
Unless you are at the top of the organizational hierarchy, there is likely to be a part of
the organization above your level that issues policy that you are expected to implement.
A common hierarchy for policy in an organization might look like this:

Enterprise-wide or Corporate Policy: the highest level (perhaps national); consists of
high-level documents that provide a direction or thrust to be implemented at lower
levels in the enterprise.

Division-wide Policy: typically consists of an amplification of enterprise-wide
policy as well as implementation guidance. This level might apply to a particular
region of a national corporation.

Local Policy: contains information specific to the local organization or corporate
element.

Issue-Specific Policy:
policy related to specific issues, e.g. firewall or anti-virus
policy.

Security Procedures and Checklists: local Standard Operating Procedures (SOPs);

derived from security policy.

Security policy may exist on some levels and not on others. Documents interact and
support one another, and generally contain many of the same elements. In a typical
organization, policy written to implement higher-level directives may not relieve
(waive) any of the requirements or conditions stipulated at a higher level. Security
policy must always be in accordance with local, state, and federal computer crime laws.

Step 2: Collect and organize the applicable written, dated, and signed policy
documents.

Now that you understand the policy hierarchy, you can collect policy documents
available at several levels in the organization. A security policy usually exists (and is
enforced to some extent) even if it is not written down. When you find instances of
unwritten policy, note them as areas for improvement. Putting the policy in writing
prevents misunderstandings and promotes right actions. Encourage your management
to articulate security policy in writing.

Step 3: Assemble existing procedures for inclusion in the policy review.
In the process of collecting policy documents, you may find procedures (perhaps issue
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specific) that do not appear to be the result of any specific policy. If so, note them for
inclusion in the policy review (discussed next).

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5. POLICY WORKSHEET

Procedures are derived from policies. A procedure can be used to identify and define
the parent policy, even if the policy is not written and signed.

ACTION: List procedures for which you need to document the policy. Make notes
on the who, what, when, and where.

Sample worksheet:
Step 1: Who does the procedure? Why?
The network administrator rolls out anti-
virus updates to local desktops.
To protect against virus infections.
Certain administrative rights are needed to
configure the push to users’ local drives.

Step 2: What is the procedure? Why?
Definitions are unpacked, and placed in a
shared directory. Login scripts download
the files, apply the update, and reboot the
machines. Machine names are flagged in
the database as having been updated

Automate the process; create an exception
list.
Step 3: When is the procedure done? Why?
The procedure is done weekly. To keep up to date with the latest virus
attacks. Our vendor rolls out new
definitions every Thursday.

Step 4: Where is the procedure done? Why?
The procedure is done from any
administrative workstation. The procedure
is applied to all desktops running Windows
9x at location XXXX.

No special location is required to apply the
procedure. All desktops need to have the
most current updates.

Step 5:
Looking at the notes from both columns, the policy becomes clear. The
description identifies the threat (virus infection) and provides for safeguards.

Sample policy derived from procedures outlined in the example above:

To ensure all desktops running Windows 9x are protected from viruses with the most recent
updates, the network administrator at each location will apply the latest virus definition updates
biweekly. Although the process can be automated, checks must be put in place to ensure the
updates have been applied successfully.

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6. EVALUATING SECURITY POLICY

PROBLEM: Your organization has a written security policy, but it is confusing,
difficult to follow, or doesn’t address one or more significant risk areas.

ACTION:
Identify policy attributes that need improvement and prepare draft
revisions.

Step 1: Verify that the security policies contain the most common elements.
Look for the following elements, and note what is missing.

Purpose

Security policy usually contains a statement, often at the beginning, describing the
reason the policy is being established, and any associated goals.

Related documents
This is often entitled “References” and usually cites higher-level policy or
implementation guidance.

Cancellation
New or updated policy may supersede existing (perhaps outdated) policy. This section
identifies those policies and clarifies what is actually in effect.

Background
This optional section is sometimes included to provide information amplifying the need
for the policy. It may also provide historical information relevant to the subject.

Scope
This section identifies the depth and breadth of coverage (to whom or what the policy
applies). Is it for one element of the organization or will it also apply to contractor
agencies who work for your organization?

Policy statement
Identifies the actual guiding principles or what is to be done. The statement(s) are
designed to influence and determine decisions and actions within the scope of coverage.
The statements should define actions that are prudent, expedient, or advantageous to
the organization.

Responsibility
The security policy document states who is responsible for what. Typical positions that
might be addressed include the head of the corporation, the CIO, people in the legal

department or in human resources, system administrators, and information security
officers. Subsections might identify how additional detailed guidance will be
developed and provided, as well as the frequency of policy review. Methods or
techniques for measuring compliance may also be included in this section (as well as
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identifying parties responsible for the audit).

Action
This section specifies what actions are necessary and when they are to be accomplished.
It may identify the time frame in which additional guidance (mentioned above) will be
forthcoming. Hopefully the policy meets the criteria stated above, but there may be a
need for a waiver process. This is one logical place to identify that process as well as
the time frame for policy review (and by whom).

Note that not all sections are required. If your search for a Policy Development Guide
was successful, consult it to determine required sections. If there is no written guide,
use the above template and check with other folks who have been successful in getting
other policy signed and implemented.

Step 2: Examine the security policy to see if it is clear.
One simple way to test for clarity is to have one of the individuals identified as being
responsible determine whether he or she understands the responsibility.

Step 3: Examine the security policy to see if it is concise
.
A specific policy topic (e.g., anti-virus signature updates) shouldn’t exceed two pages.
Many organizations limit them to one page.

Step 4: Examine the policy to see if it is realistic
.

Security policy shouldn’t require people to try to implement things that can’t be
implemented.

Government Policy

People in the United States government create some of the worst security policy in the world.
They spend taxpayer money contracting for huge notebooks of overly long, poorly written, non-
specific prose. The policy documents are so large that they cannot be updated without generating
a massive review cycle. They often require people to implement things that are not possible to
implement. Here is a brief example:
“The head of a Federal agency may employ standards for the cost effective security
and privacy of sensitive information in a Federal computer system within or under
the supervision of that agency that are more stringent than the standards
promulgated by the Secretary of Commerce, if such standards contain, at a
minimum, the provisions of those applicable standards made compulsory and
binding by the Secretary of Commerce.”

How many times did you have to read this example of
government policy before you understood what it said?
Or are you still trying?


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Step 5: Examine the policy to see if it provides sufficient guidance that a
specific procedure can be developed from it.
Policies address what is to be done and why. Procedures specify how things are done
and are how policy ultimately gets implemented. For example, if you have an Internet
connection policy, you should be able to create procedures that allow you to configure
your firewall from it. Procedures are also the basis for written checklists. Writing
guidelines or checklists is work, and people often do not wish to be bothered

documenting procedures. Many organizations have one or two employees proficient in
configuring systems, firewalls and routers. They often claim to be "too busy" to develop
written procedures. But what happens when they aren’t there?

The Bomb:

Deak Parsons was a Captain in the Navy and an Ordnance specialist. He was assigned
to the Manhattan Project during World War II. He put the first production atomic bomb
together -- but not in a lab or armory. He put it together in the bomb bay of the B-29 airplane
that dropped the first atomic bomb. He assembled it at 29,000 feet over the Pacific Ocean on the
way to Japan.
Parsons had one assistant who read to him a seven-step checklist. The checklist was a
kind of policy on how to do the job. The procedure was very stressful and risky, but it was
something he could almost do blindfolded, because of the checklist.
Good policy will reduce both stress and risk, just like the checklist did. If you
don’t have a policy (or checklist), you’ve got a time bomb on you hands waiting to go BOOM!

Step 6: Examine the policy to see if it is consistent with higher-level policy and
guidance.
If you discover any discrepancies between the policy you are reviewing and higher-
level policy, note them, as you will need to resolve them for the policy to be meaningful.
Security policy must also be in accordance with local, state, and federal computer crime
laws. Again, note any contradictions you discover so you can get the policy corrected.

Step 7: Examine the policy to see if it is forward looking.
Security policy should be open to change based on new risks and vulnerabilities,
especially following an incident. It should not be hardware- or software-specific.

Step 8: Examine the policy for provisions to keep it current.
Security policy should be reviewed regularly. Revisions in implementation should

reflect lessons learned from recent incidents and new threats to the organization’s
security. See “Action” above.

Step 9: Check to see if the security policy is readily available
.
The Policy Development Guide may provide information regarding responsibility for
publishing and making available specific policy documents. Security policy should be
incorporated in employee handbooks and posted for reference. It must be required
reading as part of the new employee orientation process.