convenient for the shopper but might not always be a secure mechanism. Users should only employ mobile payment solutions that require a per-transaction confirmation or that require the device to be unlocked and an app launched to perform a transaction. Without these precautions, it may be possible to clone your device’s contactless payment signals and perform transaction abuse.

Your organization is unlikely to see any additional risk based on mobile payment solutions. However, use caution when implementing them on company-owned equipment or when they are linked to your company’s financial accounts.

SIM Cloning

Subscriber identity module (SIM) cards are used to associate a device with a subscriber’s identity and service at a mobile or wireless telco. SIMs can be easily swapped between devices and cloned to abuse a victim’s telco services. If a SIM card is cloned, then the cloned SIMs may be able to connect other devices to the telecommunications services and link the use back to the account of the original owner. Physical control must be maintained on mobile devices and an account or service lock established on mobile services with the

telco carrier.

Essential Security Protection

Mechanisms

The need for security mechanisms within an OS comes down to one simple fact: software should not be trusted. Third-party software is inherently untrustworthy, no matter who or where it comes from. This is not to say that all software is evil. Instead, this is a protection stance—because all third-party software is written by someone other than the OS creator, that software might cause problems. Thus, treating all non-OS software as potentially damaging allows the OS to prevent many disastrous occurrences through the use of software management protection mechanisms. The OS must employ protection mechanisms to keep the computing environment stable and to keep processes isolated from one another. Without these efforts, the security of data could never be reliable or even possible. This is effectively applying the principle of zero trust (see Chapter 8).

Computer system designers should adhere to a number of common protection mechanisms when designing secure systems. These principles are specific instances of the more general security rules that govern safe computing practices. Designing security into a system during the earliest stages of development will help ensure that the overall security architecture has the best chance for success and reliability.

Process Isolation

Process isolation requires that the OS provide separate memory spaces for each process’s instructions and data. It also requires that the OS enforce those boundaries, preventing one

process from reading or writing data that belongs to another process. There are two major advantages to using this technique:

Without such controls, a poorly designed process could go haywire and write data to memory spaces allocated to other processes, causing the entire system to become unstable rather than affecting only the execution of the errant process. In a more malicious vein, processes could attempt (and perhaps even succeed at) reading or writing to memory spaces outside their scope, intruding on or attacking other processes.

Many modern OSs address the need for process isolation by implementing virtual machines on a per-user or per-process basis. A virtual machine presents a user or process with a processing environment—including memory, address space, and other key system resources and services—that allows that user or process to behave as though they have sole, exclusive access to the entire computer. This allows each user or process to operate independently without requiring it to take cognizance of other users or processes that might be active simultaneously on the same machine. As part of the mediated access to the system that the OS provides, it maps virtual resources and access in user mode so that they use supervisory mode calls to access corresponding real resources. This not only makes things easier for programmers, but also protects individual users and processes from one another.

Hardware Segmentation

Hardware segmentation is similar to process isolation in purpose—it prevents access to information that belongs to a different process/security level. The main difference is that hardware segmentation enforces these requirements through the use of physical hardware controls rather than the logical process isolation controls imposed by an OS. Such implementations are rare, and they are generally restricted to national security implementations, where the extra cost and complexity is offset by the sensitivity of the information involved and the risks inherent in unauthorized access or disclosure.

System Security Policy

Just as security policy guides the day-to-day security operations, processes, and procedures in organizations, they have an important role to play when designing and implementing systems. This is equally true whether a system is entirely hardware based, entirely software based, or a combination of both. In this case, the role of a system security policy is to inform and guide the design, development, implementation, testing, and maintenance of a particular system. Thus, this kind of security policy tightly targets a single implementation effort. (Although it may be adapted from other, similar efforts, it should reflect the target as accurately and completely as possible.)

For system developers, a system security policy is best encountered in the form of a document that defines a set of rules, practices, and procedures that describe how the system