セクション：情報資産の保護

The only way to ensure availability of all transactions is to perform a real-time transmission to an offsite facility. Choices A and B are not in real time and, therefore, would not include all the transactions. Choice C does not ensure availabilityat an offsite location.

説明／参考資料：
Explanation:
暗号化技術を用いることで、送信中のメッセージを保護することが可能です。
暗号化方式の一つであるワンタイムパッドは、正しく使用すれば解読不可能であることが証明されている。
この方式では、安全に配布された一対の鍵コードを使用し、単一のメッセージのエンコードとデコードに一度だけ使用します。ただし、この方式は安全に利用するのが難しく、非常に不便です。

Section: The process of Auditing Information System
Explanation:
Detective control helps identify an incident's activities and potentially an intruder
For your exam you should know below information about different security controls
Deterrent Controls
Deterrent Controls are intended to discourage a potential attacker. Access controls act as a deterrent to
threats and attacks by the simple fact that the existence of the control is enough to keep some potential
attackers from attempting to circumvent the control. This is often because the effort required to circumvent
the control is far greater than the potential reward if the attacker is successful, or, conversely, the negative
implications of a failed attack (or getting caught) outweigh the benefits of success. For example, by forcing
the identification and authentication of a user, service, or application, and all that it implies, the potential for
incidents associated with the system is significantly reduced because an attacker will fear association with
the incident. If there are no controls for a given access path, the number of incidents and the potential
impact become infinite. Controls inherently reduce exposure to risk by applying oversight for a process.
This oversight acts as a deterrent, curbing an attacker's appetite in the face of probable repercussions.
The best example of a deterrent control is demonstrated by employees and their propensity to intentionally
perform unauthorized functions, leading to unwanted events.
When users begin to understand that by authenticating into a system to perform a function, their activities
are logged and monitored, and it reduces the likelihood they will attempt such an action. Many threats are
based on the anonymity of the threat agent, and any potential for identification and association with their
actions is avoided at all costs.
It is this fundamental reason why access controls are the key target of circumvention by attackers.
Deterrents also take the form of potential punishment if users do something unauthorized. For example, if
the organization policy specifies that an employee installing an unauthorized wireless access point will be
fired, that will determine most employees from installing wireless access points.
Preventative Controls
Preventive controls are intended to avoid an incident from occurring. Preventative access controls keep a
user from performing some activity or function. Preventative controls differ from deterrent controls in that
the control is not optional and cannot (easily) be bypassed. Deterrent controls work on the theory that it is
easier to obey the control
rather than to risk the consequences of bypassing the control. In other words, the power for action resides
with the user (or the attacker). Preventative controls place the power of action with the system, obeying the
control is not optional. The only way to bypass the control is to find a flaw in the control's implementation.
Compensating Controls
Compensating controls are introduced when the existing capabilities of a system do not support the
requirement of a policy. Compensating controls can be technical, procedural, or managerial. Although an
existing system may not support the required controls, there may exist other technology or processes that
can supplement the existing environment, closing the gap in controls, meeting policy requirements, and
reducing overall risk.
For example, the access control policy may state that the authentication process must be encrypted when
performed over the Internet. Adjusting an application to natively support encryption for authentication
purposes may be too costly. Secure Socket Layer (SSL), an encryption protocol, can be employed and
layered on top of the authentication process to support the policy statement.
Other examples include a separation of duties environment, which offers the capability to isolate certain
tasks to compensate for technical limitations in the system and ensure the security of transactions. In
addition, management processes, such as authorization, supervision, and administration, can be used to
compensate for gaps in the access control environment.
Detective Controls
Detective controls warn when something has happened, and are the earliest point in the post-incident
timeline. Access controls are a deterrent to threats and can be aggressively utilized to prevent harmful
incidents through the application of least privilege. However, the detective nature of access controls can
provide significant visibility into the access environment and help organizations manage their access
strategy and related security risk.
As mentioned previously, strongly managed access privileges provided to an authenticated user offer the
ability to reduce the risk exposure of the enterprise's assets by limiting the capabilities that authenticated
user has. However, there are few options to control what a user can perform once privileges are provided.
For example, if a user is provided write access to a file and that file is damaged, altered, or otherwise
negatively impacted (either deliberately or unintentionally), the use of applied access controls will offer
visibility into the transaction. The control environment can be established to log activity regarding the
identification, authentication, authorization, and use of privileges on a system.
This can be used to detect the occurrence of errors, the attempts to perform an unauthorized action, or to
validate when provided credentials were exercised. The logging system as a detective device provides
evidence of actions (both successful and unsuccessful) and tasks that were executed by authorized users.
Corrective Controls
When a security incident occurs, elements within the security infrastructure may require corrective actions.
Corrective controls are actions that seek to alter the security posture of an environment to correct any
deficiencies and return the environment to a secure state. A security incident signals the failure of one or
more directive, deterrent, preventative, or compensating controls. The detective controls may have
triggered an alarm or notification, but now the corrective controls must work to stop the incident in its
tracks. Corrective controls can take many forms, all depending on the particular situation at hand or the
particular security failure that needs to be dealt with.
Recovery Controls
Any changes to the access control environment, whether in the face of a security incident or to offer
temporary compensating controls, need to be accurately reinstated and returned to normal operations.
There are several situations that may affect access controls, their applicability, status, or management.
Events can include system outages, attacks, project changes, technical demands, administrative gaps, and
full-blown disaster situations. For example, if an application is not correctly installed or deployed, it may
adversely affect controls placed on system files or even have default administrative accounts unknowingly
implemented upon install.
Additionally, an employee may be transferred, quit, or be on temporary leave that may affect policy
requirements regarding separation of duties. An attack on systems may have resulted in the implantation of
a Trojan horse program, potentially exposing private user information, such as credit card information and
financial data. In all of these cases, an undesirable situation must be rectified as quickly as possible and
controls returned to normal operations.
The following answers are incorrect:
Deterrent - Deterrent controls are intended to discourage a potential attacker
Preventive - Preventive controls are intended to avoid an incident from occurring
Compensating - Compensating Controls provide an alternative measure of control
The following reference(s) were/was used to create this question:
CISA Review Manual 2014 Page number 44
and
Official ISC2 CISSP guide 3rd edition Page number 50 and 51