vectors.

Threat Determination

Your goal for the purposes of establishing a business case for intrusion detection is to list wellknown, probable threats as opposed to all threats. How do you find these threats? Sources might include the following:

∙Newspaper or web articles on attacks at other places. If it happens to them, it could happen to you.

∙Firewall/intrusion-detection logs for specific threats.

∙System audit trail logs.

∙Demonstration of an intrusion-detection system.

Many commercial intrusion-detection vendors allow you to take their systems for a test drive, with a 30-day trial or something similar. If you are serious about wanting to implement an IDS capability, I can't stress how important this is to do. It gives you a list of actual attacks against your network; this is helpful for establishing the threat. It helps establish the groundwork for part three of the plan when you show why you recommend an intrusion-detection system as opposed to, say, another firewall. And, it gives you experience with a couple commercial offerings. All too often, folks make their decision either based on something they read or on how friendly the salesperson is. If you have tried a few "loaner" IDSs, in part three of the plan, you can make honest statements about the tradeoffs between various systems.

If you can find the time to do it, interviews with folks in various parts of your organization can be a rich source of threats and vulnerabilities that you might otherwise have missed. I have had people tell me about shockingly bad practices when I ask them what they consider the largest dangers to the organization's information assets to be. Yet, they never came forward with the information on their own. As they say in Alabama, "Whaay-el, you never asked."

Asset Identification

Chapter 17 discussed asset valuation. Now, you focus on the concept a bit more. The huge value is the investment in data. If most of your workers use computers most of their workday, the value of the data on the computer is the cost of putting that worker in front of the console. The threats to that data are that it will be copied, destroyed, or modified.

We have touched on this throughout the book. So that we are really clear, however, I will reiterate: The most probable threat to that data is destruction from the system owner. As my Catholic friends would point out, this could be by a sin of commission, or a sin of omission. By commission, I mean an overt act, deleting the data accidentally, or on purpose, and never telling anyone so that it can be recovered. By omission, I mean the failure to back up the data properly, and that includes off-site backup. At least for the things that are within your power to change, work to ensure your data is backed up.

It turns out to be an almost impossible task to ensure that all the data throughout the organization is protected from being copied, destroyed, or modified. In the same way, making sure every data element is backed up, on and off site, is beyond the capabilities of any

organization that I know of. This is a great lead-in to the notion of crown jewels, or critical program information (CPI) as they say in security texts.

Valuation

All your data is not of the same value. In fact, a small portion of the information that exists in your organization is what distinguishes you from your competition. Although all your data has value, crown jewels are the information that has critical value and must be protected.

You reflect this in the threat section of your plan. Find as many of the crown jewels as possible. Consider the threat vectors, and the known common threats, and use these as the examples of threats and vulnerabilities in part two of your intrusion-detection business plan.

In part three, you will discuss countermeasures to protect these clusters of high-value information. These might include the following:

∙Host-based IDS software on the critical systems.

∙Honeypot files. If your organization has sensitive documents, you can add special tagged strings into the document. One way to do this is invent acronyms that do not actually exist. Then you can program your IDS watch for these with a string, or content matching rule. This would tell you if these files are entering or leaving your network.

∙Instrumenting internal systems with personal firewalls. (Technically oriented employees often enjoy doing this.)

∙Network-based IDS in high-value locations.

Vulnerability Analysis

Vulnerabilities are the gateways by which threats are made manifest. All the threats in the world don't matter if there are no vulnerabilities.

Were you disappointed because I didn't give a long list of vulnerabilities from which to work? Well, they change almost daily so you need a pointer to a current list, not a static one that will

be obsolete before the book is even printed. I like the Computer Vulnerabilities and Exposures (CVE) project (cve.mitre.org) the best because it cross-indexes a number of great

vulnerability lists such as bugtraq and ISS's X-Force. However, you do not need to do this manually. Getting your general threat list as well as an assessment of your vulnerabilities is a fairly simple matter. A number of good vulnerability assessment tools are available. These tools test for specific threats, and they find potential vulnerabilities. Let's consider three classes of tools: system-vulnerability scanners, network-based scanners, and also phone-line scanners.

Tools such as COPS, SPI, tiger, and STAT are examples of system-vulnerability scanners. They work within the system looking for missing patches, incorrectly set file permissions, and similar problems.

Tools such as nmap, nessus, saint, ISS' Internet Scanner, and Axent's NetRecon are examples of network-based scanners. These are fairly fast and effective and scan the network looking for unprotected ports or services.

While conducting vulnerability assessments, you might also want to assess your risk from the attackers who scan your phone lines looking for active modems. Toneloc, available from fine hacking sites everywhere, is the most used tool for this. Phonesweep from http://www.sandstorm.net is a commercial tool with some additional features.

If at all possible, your vulnerability assessment should offer three views:

∙A system view. Taken from selected systems with system scanners.

∙A network view. Done from an internal scan of your network.

∙An Internet view. Done from outside your firewall and, if possible, a phone scan as well.

Of course, you want some juicy vulnerabilities to spice up your report, but please also scan your firewall, DNS, mail, and web servers, as well as systems related to your crown jewels. These are the systems that your organization depends on.

Whew! Sounds like a lot of work, doesn't it? Correct, it is a lot of work and vulnerability assessments are not something that should be done only once. Why does it make sense for the intrusion-detection analyst to be involved in vulnerability assessments? It keeps you aware of specific problems and where in the organization your vulnerabilities are located.

Risk Evaluation

You have a lot of data. What do you do with it? Just because you collected it, do not stuff it all in your report, even as labeled appendixes. On the other hand, you do want it organized and available. Whenever you brief senior management, you want at least one supporting layer of data available—that is, if your slide says 12 systems are deemed to contain CPI, you darn sure want to be able to list those systems and explain the rationale for choosing them and not others.

Okay, we have answered the question of what you are not going to put in the second section of the report. What should you provide?

∙A top-level slide with the value of the organization's information assets. Suppose you have 100 computers with a five-year life cycle, for instance. The hardware, software, and maintenance costs are $200k/year with information valued at $1 million.

∙A network diagram that defines the boundary you are trying to protect.

∙A basic description of the threat vectors.

∙A general summary of your general vulnerability assessment.

∙A description of the crown jewels: where they are, their value, and so on (include the firewall, DNS, mail, and web servers).

∙Specific threats against the crown jewels.