A remote access e-mail gateway will enable your employees to get to their e-mail while they’re away from the office. However, this same gateway can also provide intruders with a side door to your network. Likewise, a FTP server will enable customers anywhere in the where instantly to get fixes for your software products. On the other hand, intruders might use your ftp server as an electronic tunnel to valuable corporate data.
With worldwide connections, someone can get into your system in the middle of the night when your building is locked up. The Internet allows the electronic equivalent of an intruder who looks for open windows and doors. Now, a person can check for hundreds of vulnerabilities in just a few hours.
Every organization requires some type of a network site security policy. This will serve to protect its valuable assets — everything from systems to data. The policy guidelines presented here will help you to establish an enterprise-wide program of how both internal and external users interact with a company’s computer network, how the corporate computer architecture topology will be implemented, and where computer assets will be located.
To create a good site policy for computer security, you’ll need to do two things: determine the expectations of proper computer and network use, and the procedures to prevent and respond to security incidents. To this end, you, working with your policy committee, need also to consider and to agree upon the following:
- The organization’s goals and direction. A university with building spread across a large campus will have different security concerns than a corporation in an office park.
- The site security policy has to conform to existing policies, rules, regulations, and laws the organization must adhere to. You’ll, therefore, have to identify and consider these things while you develop the policy.
- If your network extends outside your facility, you’ll have to consider security on perhaps a global scale. The policy should address local security issues caused by a remote site, as well remote system security issued caused by a local host or user.
Next, you’ll need to look at whom, besides yourself, will devise the network site security policy. Policy creation should consist of a representative group of decision makers, technical personnel, and day-to-day users from different levels within the organization. Decision makers should have the power to enforce the policy. Technical personnel should advise on the ramifications of the policy. Likewise, day-to-day users should have a say in how easy or difficult the policy will be to carry out.
Developing a security policy requires that you identify the organizational assets, identify the threats, evaluate the risk, evaluate and implement the tools and technologies available to meet the risks, and develop a usage policy. In addition, you’ll need to devise audit procedures for how to do timely reviews of the network and server usage, and how to respond to violations or breakdown. Finally, you’ll need to communicate information the policy to everyone (both employees and contractors) who uses the computer network. Plan to review the policy regularly.
Identifying Your Organization’s Assets
Your very first step in creating a site security policy consists of compiling a comprehensive list of all the things that need to be protected.
Items to consider include:
- personal computers
- disk drives
- communication lines
- terminal servers
- source programs
- object programs
- diagnostic programs
- operating systems
- communication programs
- during execution
- stored on-line
- archived off-line
- audit logs
- in transit over communication media
- people needed to run systems
- programs & applications
- local administrative procedures
- magnetic media
Evaluating the Risks
Risk analysis involves determining what you’ll need to protect, what you’ll need to protect it from, and how to protect it. This process forces you to examine all of your risks, ranking each one by severity level.
Possible risks to your network include:
- Unauthorized access.
- Unavailable service, which can include some or all network services, corruption of data, or a slowdown due to a virus.
- Disclosure of sensitive information, especially that which gives someone else a particular advantage, or theft of information such as credit card information.
Once you’ve put the list together, then you’ll need a scheme for weighing the risk against the importance of the resource. This exercise will enable the site policy makers to determine how much effort to spend protecting the resource.
Defining a Policy for Acceptable Use
To define a policy for how users will interact with the network, you’ll need to consider the following in a policy for acceptable use:
- Who is allowed to use the resources?
- What is the proper use of the resources?
- Who is authorized to grant access and approve usage?
- Who may have system administration privileges?
- What are the users’ rights and responsibilities?
- What are the rights and responsibilities of the system administrator vs. those of the user?
- What do you do with sensitive information?
For example, you’ll want to cover the following topics when defining the users’ rights and responsibilities:
- What guidelines you have regarding resource consumption (whether users are restricted, and if so, what the restrictions are).
- What might constitute abuse in terms of system performance.
- Whether users are permitted to share accounts or let others use their accounts.
- What level of secrecy users should apply to their login/password information.
- How often users should change their passwords and any other password restrictions or requirements.
- Whether you provide backups or expect the users to create their own.
- Disclosure of information that may be proprietary.
- Statement on Electronic Mail Privacy (Electronic Communications Privacy Act). Specifically, does the company consider electronic mail private to each employee, or do they consider it the property of the organization?
- Your policy concerning mail or postings to mailing lists or discussion groups (obscenity, harassment, etc.), and on representing the organization to these areas.
- Policy on electronic communications: mail forging, etc.
You’ll also need to define who’ll interpret the policy – an individual or a committee. No matter how well written, the policy will require interpretation from time to time, and this body will serve to review, to interpret, and to revise the policy as needed.
Auditing and Reviewing
To help determine if there is a violation of your security policy, you’ll need to depend on the tools included with your computer and network. Most operating systems store numerous bits of information in log files. Examining these log files regularly will often provide the first line of defense for detecting unauthorized use of the system.
- Compare lists of currently logged in users and past login histories. Most users typically log in and out at roughly the same time each day. An account logged in outside the normal time for the account may be in use by an intruder.
- Many systems maintain accounting records for billing purposes. These records can also be used to determine usage patterns for the system; unusual accounting records may indicate unauthorized use of the system.
- System logging facilities, such as the UNIX syslog utility, should be checked for unusual error messages from system software. For example, a large number of failed login attempts in a short period of time may indicate someone trying to guess passwords.
- Operating system commands which list currently executing processes can be used to detect users running programs they are not authorized to use, as well as to detect unauthorized programs which have been started by an intruder.
By running various monitoring commands at different times throughout the day, you’ll make it hard for an intruder to predict your actions. While it may be exceptionally fortuitous that an administrator would catch a violator in their first act, by reviewing log files you’ll have a very good chance setting up procedures to identify them at a later date.
Security is a dynamic process. Since it’s getting easy to break into network sites through easily available, point-and-click packages, you’ll need to do regularly reviews of your network. To this end, you’ll need to assemble the core team or a representative subset to review how well things are working, what are the latest threats and security tools, and what are the risks against new assets and business practices.
In the conclusion of this article, we’ll look at some of the preventative measures you can take, as well as how to respond to violations.
Elizabeth M. Ferrarini is a free-lance writer based in Arlington, Massachusetts.