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A financial institution can significantly mitigate the risk of security events by an appropriate technology design that provides for effective network-level monitoring, limits an intruder's ability to traverse the network, offers the minimum level of services required for business needs, and is updated in a timely manner to mitigate newly discovered vulnerabilities.
An effective means of accomplishing those goals is through the use of security domains. A security domain is a part of the system with its own policies and control mechanisms. Security domains for a network are typically constructed from routing controls and directories.
Domains constructed from routing controls may be bounded by network perimeters with perimeter controls. The perimeters separate what is not trusted from what may be trustworthy. The perimeters serve as well-defined transition points between trust areas where policy enforcement and monitoring takes place. An example of such a domain is a demilitarized zone (DMZ), bounded by a perimeter that controls access from outside and inside the institution.
Domains constructed from directories may limit access to network resources and applications based on role or function. Directory-driven domains may allow access to different network-driven domains. For example, a network management domain may use the same cabling and network interface cards as other domains, allow access to all computing devices in all domains, but limit the allowed access based on the user's role or function.
The selection of where to put which control is a function of the risk assessment. Institutions generally should establish defenses that address the network and application layers at external connections, whether from the Internet or service providers. Internally, perimeters can be established at higher-risk security domains, such as wire transfer, and to segregate at a network level those areas of the institution that work with customer information from other areas. Internal perimeters also may be used to create security domains based on geography or other logical or physical separations.
Hosts may also include security perimeters. Those perimeters are enforced through authorizations for users and programs. The authorizations can be a part of applications, the file system, and the operating system.