weekly review of lower logs may be the key to detecting advanced persistent threats or other intrusions . Monitoring the network will aid in the eventual changes that must occur within the architecture, and while it may not be particularly exciting, it is pivotal to a good security architecture .
Maintain the architecture and adapt it as new attack vectors and surfaces become available. Maintenance is not only the method by which new signatures are installed and patches applied, but the maintenance of the architecture itself is also necessary to securing the network . Trends like “bring your own device” create serious challenges to the security architecture as it may remove a key bottleneck from your administration . Implementing security controls that quarantine and evaluate new nodes may become a part of the architecture and these new nodes may introduce a horde of new vulnerabilities and threats to your network . Maintenance is also the catalyst for determining the lifecycle of a control—while a perimeter firewall may last three to five years, the host-based firewall may be changed yearly. Use the habits from the monitoring section to decide how to best maintain your security controls. Remember that the physical devices themselves should not be forgotten as they may also fail . Figure 4 shows how each of these pillars is used to form a new defense methodology that is made up of essential security practices rather than checklists and abstracts.
The various methods of defense purport benefits and entail consequences that may be counterproductive in practice. An administrator should design a security posture around essential elements and use either defense in depth or defense in breadth as a guideline. Understanding the components and elements of each methodology will help an administrator make a more informed choice; however, the target network must also be considered to ensure that the correct methodology is implemented . As an administrator, you must consider all options and perhaps elements of both the defense in depth and defense in breadth methodologies appeal to and suit your network. Also consider that a hybrid method may be the most favorable of all [9,19].
There are pitfalls to a security architecture design that must be avoided. Haphazardly purchasing and setting up security technologies often will not improve security at all and may even weaken it . Having a carefully considered plan is the first step to design an information defense strategy. Just as important as the plan is the human aspect to security. Understand the human asset constraints that exist in your network. If you know that your organization is exclusively five days a week and 9 to 5 then steps must be taken to ensure that the information assets remain protected and intrusions can be prevented in the off hours. Vulnerabilities in human assets are just as dangerous as those in our information systems .
When possible, administrators should choose team members who are motivated and interested in the field of information security. Team members should be interested in learning as the field of information security is constantly evolving, and complacency leads to weakness. Security administrators should understand that higher education in team members is exceedingly valuable; the foundations of information security cannot be imparted in on-the-job training. Choose well-rounded security professionals who combine industry certifications with experience and education. Treat human resources just like any other security control, and choose a good product that requires minimal overhead and yields the greatest benefit to the security posture.
Security postures and methodologies are constantly changing and improving. Often it may be more productive to examine what makes a methodology appealing and use that to create or improve the organization’s posture. Fortify, Disperse, Diversify, Monitor, and Maintain: these elements are outlined in this paper as key pillars in a defense methodology and should be included in some fashion in all security postures. Adding additional pillars only strengthens the organization’s posture, so carefully
Figure 4. Pillars of a good defense methodology.
consider what factors are most important to your particular network and design your security posture around those factors. To begin to understand your network, evaluate the data and resources that is the most essential to your organization’s survival. Tactically it is sound to group your most precious assets in the most defendable position inside the network . Layering defenses can be beneficial to the security posture if it is done with a conscious goal and in such a way that it provides more functionality than overhead .
There simply is no cookie cutter security template that you can just apply to your network and generate a shopping list of technologies for application. Defense in Depth was never designed to function as a magical solution, and too much emphasis has been placed on the methodology and not enough on the actual concepts involved [4,19]. The defense in depth methodology is only a set of best practices, and like this paper it aims to inform administrators and aid them in designing the best security posture for their organization . The public failings of information security in high-profile organizations led some to blame Defense in Depth and propose Defense in Breadth [9,10,12]. Defense in Breadth does add beneficial concepts to the Defense in Depth methodology; however, it also does not magically solve all information security issues. Administrators should evaluate security methodologies only as best practices and utilize them as resources and not a master plan.