The correct answer is Maintenance window because firmware upgrades on critical infrastructure devices, such as routers, must be performed during a predefined and approved time period to minimize operational impact.
Within the Security+ SY0-701 objectives, maintenance windows are a key component of change management and operational security, ensuring that potentially disruptive changes occur when business risk is lowest.
Upgrading router firmware often requires rebooting the device, which can temporarily interrupt network connectivity. A maintenance window defines when this downtime is acceptable, ensures stakeholders are notified in advance, and allows rollback plans to be executed if the upgrade fails. The SY0-701 study guide stresses that scheduled maintenance windows reduce the risk of unplanned outages, service-level agreement violations, and user disruption while supporting system stability and availability.
Option A, Software development life cycle, applies to the design, development, testing, and deployment of software applications, not routine infrastructure maintenance tasks like firmware updates. Option B, Risk tolerance, refers to an organization's willingness to accept risk and guides decision-making at a strategic level, but it does not dictate the procedural steps of performing an upgrade. Option C, Certificate signing request, is used when requesting digital certificates from a certificate authority and is unrelated to firmware updates.
Following a maintenance window aligns with best practices emphasized in SY0-701 for managing operational risk, preserving availability, and enforcing structured change control. It ensures proper approvals, testing, monitoring, and backout plans are in place before changes are introduced into production environments.
In summary, firmware upgrades are operational changes that can affect availability. Performing them during an approved maintenance window is essential to maintaining reliable network operations and reflects Security+ SY0-701 best practices for secure and controlled system management.

Port 445 is used by the SMB protocol on Windows systems. Large volumes of unexpected traffic on TCP 445 are commonly associated with worms that exploit SMB vulnerabilities (such as WannaCry or NotPetya).
Worms are self-replicating malware that spread rapidly across a network, consuming bandwidth, causing high latency, and often resulting in network outages. This matches the scenario given, where network unavailability and abnormal port 445 traffic are observed.
References:
CompTIA Security+ SY0-701 Official Study Guide, Domain 2.1, "Malware Types: Worms" CompTIA Security+ Exam Objectives: 2.1 CompTIA Glossary: "Worm-A self-replicating malware that spreads across networks, often exploiting vulnerabilities such as those in SMB (TCP 445)."