Copyright(c) Management Analytics, 1995 - All Rights Reserved

1.1 Purpose of this Work

This handbook is a guide to setting computer security policies and procedures for sites that have systems on the Internet. This guide lists issues and factors that a site must consider when setting their own policies. It makes some recommendations and gives discussions of relevant areas.

This guide is only a framework for setting security policies and procedures. In order to have an effective set of policies and procedures, a site will have to make many decisions, gain agreement, and then communicate and implement the policies.

1.2 Audience

The audience for this work are system administrators and decision makers (who are more traditionally called "administrators" or "middle management") at sites. This document is not directed at programmers or those trying to create secure programs or systems. The focus of this document is on the policies and procedures that need to be in place to support any technical security features that a site may be implementing.

The primary audience for this work are sites that are members of the Internet community. However, this document should be useful to any site that allows communication with other sites. As a general guide to security policies, this document may also be useful to sites with isolated systems.

1.3 Definitions

For the purposes of this guide, a "site" is any organization that owns computers or network-related resources. These resources may include host computers that users use, routers, terminal servers, PC's or other devices that have access to the Internet. A site may be a end user of Internet services or a service provider such as a regional network. However, most of the focus of this guide is on those end users of Internet services.

We assume that the site has the ability to set policies and procedures for itself with the concurrence and support from those who actually own the resources.

The "Internet" is those set of networks and machines that use the TCP/IP protocol suite, connected through gateways, and sharing a common name and address spaces [1].

The term "system administrator" is used to cover all those who are responsible for the day-to-day operation of resources. This may be a number of individuals or an organization.

The term "decision maker" refers to those people at a site who set or approve policy. These are often (but not always) the people who own the resources.

1.4 Related Work

The IETF Security Policy Working Group (SPWG) is working on a set of recommended security policy guidelines for the Internet [23]. These guidelines may be adopted as policy by regional networks or owners of other resources. This handbook should be a useful tool to help sites implement those policies as desired or required. However, even implementing the proposed policies isn't enough to secure a site. The proposed Internet policies deal only with network access security. It says nothing about how sites should deal with local security issues.

1.5 Scope

This document covers issues about what a computer security policy should contain, what kinds of procedures are need to enforce security, and some recommendations about how to deal with the problem. When developing a security policy, close attention should be made not only on the security needs and requirements of the local network, but also the security needs and requirements of the other interconnected networks.

This is not a cookbook for computer security. Each site has different needs; the security needs of a corporation might well be different than the security needs of an academic institution. Any security plan has to conform to the needs and culture of the site.

This handbook does not cover details of how to do risk assessment, contingency planning, or physical security. These things are essential in setting and implementing effective security policy, but this document leaves treatment of those issues to other documents. We will try to provide some pointers in that direction.

This document also doesn't talk about how to design or implement secure systems or programs.

1.6 Why Do We Need Security Policies and Procedures?

For most sites, the interest in computer security is proportional to the perception of risk and threats.

The world of computers has changed dramatically over the past twenty-five years. Twenty-five years ago, most computers were centralized and managed by data centers. Computers were kept in locked rooms and staffs of people made sure they were carefully managed and physically secured. Links outside a site were unusual. Computer security threats were rare, and were basically concerned with insiders: authorized users misusing accounts, theft and vandalism, and so forth. These threats were well understood and dealt with using standard techniques: computers behind locked doors, and accounting for all resources.

Computing in the 1990's is radically different. Many systems are in private offices and labs, often managed by individuals or persons employed outside a computer center. Many systems are connected into the Internet, and from there around the world: the United States, Europe, Asia, and Australia are all connected together.

Security threats are different today. The time honored advice says "don't write your password down and put it in your desk" lest someone find it. With world-wide Internet connections, someone could get into your system from the other side of the world and steal your password in the middle of the night when your building is locked up. Viruses and worms can be passed from machine to machine. The Internet allows the electronic equivalent of the thief who looks for open windows and doors; now a person can check hundreds of machines for vulnerabilities in a few hours.

System administrators and decision makers have to understand the security threats that exist, what the risk and cost of a problem would be, and what kind of action they want to take (if any) to prevent and respond to security threats.

As an illustration of some of the issues that need to be dealt with in security problems, consider the following scenarios (thanks to Russell Brand [2, BRAND] for these):

1.7 Basic Approach

Setting security policies and procedures really means developing a plan for how to deal with computer security. One way to approach this task is suggested by Fites, et. al. [3, FITES]:

This handbook will concentrate mostly on the last two steps, but the first three are critically important to making effective decisions about security. One old truism in security is that the cost of protecting yourself against a threat should be less than the cost recovering if the threat were to strike you. Without reasonable knowledge of what you are protecting and what the likely threats are, following this rule could be difficult.

1.8 Organization of this Document

This document is organized into seven parts in addition to this introduction.

The basic form of each section is to discuss issues that a site might want to consider in creating a computer security policy and setting procedures to implement that policy. In some cases, possible options are discussed along with the some of the ramifications of those choices. As far as possible, this document tries not to dictate the choices a site should make, since these depend on local circumstances. Some of the issues brought up may not apply to all sites. Nonetheless, all sites should at least consider the issues brought up here to ensure that they do not miss some important area.

The overall flow of the document is to discuss policy issues followed by the issues that come up in creating procedures to implement the policies.

Section 2 discusses setting official site policies for access to computing resources. It also goes into the issue of what happens when the policy is violated. The policies will drive the procedures that need to be created, so decision makers will need to make choices about policies before many of the procedural issues in following sections can be dealt with. A key part of creating policies is doing some kind of risk assessment to decide what really needs to be protected and the level of resources that should be applied to protect them.

Once policies are in place, procedures to prevent future security problems should be established. Section 3 defines and suggests actions to take when unauthorized activity is suspected. Resources to prevent secruity breaches are also discussed.

Section 4 discusses types of procedures to prevent security problems. Prevention is a key to security; as an example, the Computer Emergency Response Team/Coordination Center (CERT/CC) at Carnegie- Mellon University (CMU) estimates that 80% or more of the problems they see have to do with poorly chosen passwords.

Section 5 discusses incident handling: what kinds of issues does a site face when someone violates the security policy. Many decisions will have to made on the spot as the incident occurs, but many of the options and issues can be discussed in advance. At very least, responsibilities and methods of communication can be established before an incident. Again, the choices here are influenced by the policies discussed in section 2.

Section 6 deals with what happens after a security violation has been dealt with. Security planning is an on-going cycle; just after an incident has occurred is an excellent opportunity to improve policies and procedures.

The rest of the document provides references and an annotated bibliography.