The sampling method in which the entire sample is considered to be irregular if a single error is found is discovery sampling. Discovery sampling is a type of statistical sampling that is used to test for the existence of at least one occurrence of a specific characteristic or condition in a population. Discovery sampling is often used when the auditor expects the characteristic or condition to be very rare or nonexistent, and when any occurrence would have a significant impact on the audit objective. For example, discovery sampling can be used to test for fraud, noncompliance, or material misstatement.
Discovery sampling works by setting a very low tolerable error rate (the maximum rate of occurrence of the characteristic or condition that the auditor is willing to accept) and a high confidence level (the degree of assurance that the auditor wants to obtain). The auditor then selects a sample from the population using a random or systematic method, and examines each item in the sample for the presence or absence of the characteristic or condition. If no error is found in the sample, the auditor can conclude with a high level of confidence that the characteristic or condition does not exist or is very rare in the population. However, if one or more errors are found in the sample, the auditor cannot draw any conclusion about the population and must either expand the sample size or perform alternative procedures.
Discovery sampling differs from other sampling methods in that it does not allow for any errors in the sample.
Other sampling methods, such as variable sampling, stop-or-go sampling, or judgmental sampling, can tolerate some errors in the sample and use them to estimate the error rate or amount in the population. However, discovery sampling is designed to test for zero-tolerance situations, where any error would be unacceptable or material. Therefore, discovery sampling considers the entire sample to be irregular if a single error is found.
References:
* Audit Sampling - Overview, Purpose, Importance, and Types1
* Audit Sampling - What Is It, Methods, Example, Advantage, Reason2
* ISA 530: Audit sampling | ICAEW3
* Audit Sampling - AICPA4

Explanation/Reference:
With the objective of mitigating the risk and impact of a major business interruption, a disaster-recovery plan should endeavor to reduce the length of recovery time necessary and the costs associated with recovery. Although DRP results in an increase of pre-and post-incident operational costs, the extra costs are more than offset by reduced recovery and business impact costs.

Section: Protection of Information Assets
Explanation:
In addition to deploying stateful firewall, you may setup basic traffic filtering on a more sophisticated router.
As an example, on a Cisco IOS based router you may use ip access lists (ACL) to perform basic filtering on
the network edge. Note that if they have denied too much traffic, something is obviously being too
restrictive and you may want to reconfigure them.

A cold site is often an acceptable solution for preparing for recovery of noncritical systems and datA .