issues are handled by encryption and hashing, please see Chapters 6 and 7 for those topics. Other important characteristics are transparency, logging, and error management.

Transparency

Just as the name implies, transparency is the characteristic of a service, security control, or access mechanism that ensures that it is unseen by users. Transparency is often a desirable feature for security controls. The more transparent a security mechanism is, the less likely a user will be able to circumvent it or even be aware that it exists. With transparency, there is a lack of direct evidence that a feature, service, or restriction exists, and its impact on performance is minimal.

In some cases, transparency may need to function more as a configurable feature than as a permanent aspect of operation, such as when an administrator is troubleshooting, evaluating, or tuning a system’s configurations.

Transmission Management Mechanisms

Transmission logging is a form of auditing focused on communications. Transmission logging records the particulars about source, destination, time stamps, identification codes, transmission status, number of packets, size of message, and so on. These pieces of information may be useful in troubleshooting problems and tracking down unauthorized

communications or used against a system as a means to extract data about how it functions. Transmission error correction is a capability built into connectionor session-oriented protocols and services. If it is determined that a message, in whole or in part, was corrupted,

altered, or lost, a request can be made for the source to resend all or part of the message. Retransmission controls determine whether all or part of a message is retransmitted in the event that a transmission error correction system discovers a problem with a communication. Retransmission controls can also determine whether multiple copies of a hash total or CRC (cyclic redundancy check) value are sent and whether multiple data paths or communication channels are employed.

Prevent or Mitigate Network Attacks

Communication systems are vulnerable to attacks in much the same way any other aspect of the IT infrastructure is vulnerable. Understanding the threats and possible countermeasures is an important part of securing an environment. Any activity or condition that can cause harm to data, resources, or personnel must be addressed and mitigated if possible. Keep in mind that harm includes more than just destruction or damage; it also includes disclosure, access delay, denial of access, fraud, resource waste, resource abuse, and loss. Common threats against communication system security include DoS (see Chapter 17, “Preventing and Responding to Incidents”), impersonation (see Chapter 2), replay (see Chapter 11), ARP poisoning (see Chapter 11), DNS poisoning (see Chapter 11), eavesdropping, and transmission modification.