When a critical component like a generator fails during a business continuity tabletop

exercise, the security team's concern about "potential impacts" directly relates to the

duration of the outage caused by this failure. Mean Time To Repair (MTTR) is the

specific metric that quantifies how long it will take to repair or restore the failed

generator. Considering the MTTR is a crucial risk management activity because it helps

the team estimate the length of the disruption, determine if Recovery Time Objectives

(RTOs) for dependent systems can still be met, and thereby assess the severity of the

business impact. Understanding the MTTR is essential for making informed decisions

about immediate response and recovery actions.

· A. RPO (Recovery Point Objective): RPO defines the maximum acceptable amount

of data loss measured in time. While a prolonged outage due to generator failure

could indirectly affect data, RPO is not the primary consideration for the impact of the

generator's downtime itself.

· B. ARO (Annualized Rate of Occurrence): ARO estimates how often a particular

event (like a generator failure) is expected to occur within a year. This is relevant for

long-term risk assessment but not the immediate consideration when dealing with the

impacts of an active failure in an exercise.

· C. BIA (Business Impact Analysis): A BIA is a broader analysis to identify and

quantify the potential impacts of disruptions on business functions and is used to

determine RTOs. While the team is concerned about impacts (which the BIA helps

define), the MTTR of the generator is a critical, specific input needed during the event to

understand the duration that leads to those impacts. The BIA provides the context for

impact, but MTTR is the immediate factor related to the generator's failure.

1. NIST Glossary - Mean Time To Repair (MTTR):

o URL: https://csrc.nist.gov/glossary/term/mean_time_to_repair

o Definition: "The average time to restore a system to full operational status after a

failure or incident."

o Relevance: This definition supports why MTTR is considered when assessing the

downtime of the failed generator.

2. NIST Special Publication 800-34 Rev. 1, "Contingency Planning Guide for

Federal Information Systems":

o URL: https://doi.org/10.6028/NIST.SP.800-34r1

o Section 3.2 (Business Impact Analysis), Page 13: "The BIA is a key step in the

contingency planning process... A BIA assists in identifying the potential consequences

of an information system disruption... The BIA should identify the MTD [Maximum

Tolerable Downtime] for information system resources. The MTD is then used to

establish recovery time objectives (RTOs)."

o Relevance: This explains BIA's role in identifying consequences and setting

recovery objectives (RTOs). The MTTR of a component like a generator directly

influences whether these RTOs can be met. If a generator fails, its MTTR will

determine the duration of power loss, which is then assessed against the impacts outlined

in the BIA for that duration.

3. NIST Special Publication 800-53 Rev. 5, "Security and Privacy Controls

for Information Systems and Organizations":

o URL: https://doi.org/10.6028/NIST.SP.800-53r5

o Control CP-2 (Contingency Plan), Discussion: Mentions that contingency plans

address recovery objectives. Control CP-7 (Alternate Processing Site) and CP-8

(Telecommunications Services) imply the need for recovery capabilities which

inherently involve considerations of recovery time for components.

o Relevance: The ability to meet recovery objectives, which are part of risk

management and contingency planning, depends on the recovery times of critical

components (related to their MTTR).