The primary purpose of classifying and categorizing security incidents is to establish a framework for prioritization and response. Incident impact is the most appropriate factor because it directly measures the adverse effect of an incident on business operations, assets, and objectives. A classification scheme based on impact (e.g., high, medium, low) ensures that incidents with the greatest potential to disrupt the business, cause financial loss, or damage reputation receive the highest priority and the most appropriate level of resources. This aligns incident response activities directly with the organization's risk tolerance and business protection goals.

A. Maturity of incident response activities: This describes the capability of the response team, not the characteristics of the incident itself, which is what classification is based on.

B. Threat environment: This informs the types of incidents an organization might face, but the classification level is determined by the potential damage (impact) of those incidents.

C. Quantity of impacted assets: This is only one component of impact. The compromise of a single, highly critical asset can have a far greater impact than many non-critical ones.

1. National Institute of Standards and Technology (NIST) Special Publication 800-61 Rev. 2

Computer Security Incident Handling Guide. Section 2.3.3

"Incident Prioritization

" states

"Incidents should be prioritized based on the relevant factors

such as the functional impact of the incident (e.g.

current and likely future negative impact to business functions)

the information impact of the incident (e.g.

effect on the confidentiality

integrity

and availability of the organization’s information)

and the recoverability from the incident." This directly ties prioritization

which is the outcome of classification

to impact.

2. ISACA

CISM Review Manual

16th Edition. In the domain of Information Security Incident Management

the manual consistently emphasizes that incident classification and subsequent prioritization must be based on business impact. It states that the objective is to manage incidents in accordance with their potential or actual effect on the confidentiality

integrity

and availability of information assets and the resulting impact on the business.

3. Peltier

T. R. (2013). Information Security Risk Analysis

Third Edition. CRC Press. Chapter 7

"Risk Assessment and Analysis

" discusses how the impact of an event is a critical component in determining its overall risk and severity. This principle is applied directly to incident management

where the classification of an incident is a function of its measured or potential impact on the organization.