The most critical finding for an IS auditor following up on a recent security incident is that the security weakness facilitating the attack was not identified. This finding indicates that the root cause of the incident was not analyzed, and the vulnerability that allowed the attack to succeed was not remediated. This means that the organization is still exposed to the same or similar attacks in the future, and its security posture has not improved. Identifying and addressing the security weakness is a key step in the incident response process, as it helps to prevent recurrence, mitigate impact, and improve resilience.
The other findings are not as critical as the failure to identify the security weakness, but they are still important issues that should be addressed by the organization. The attack was not automatically blocked by the intrusion detection system (IDS) is a finding that suggests that the IDS was not configured properly, or that it did not have the latest signatures or rules to detect and prevent the attack. The attack could not be traced back to the originating person is a finding that implies that the organization did not have sufficient logging, monitoring, or forensic capabilities to identify and attribute the attacker. Appropriate response documentation was not maintained is a finding that indicates that the organization did not follow a consistent and formal incident response procedure, or that it did not document its actions, decisions, and lessons learned from the incident.
References:
* ISACA CISA Review Manual 27th Edition (2019), page 254
* Incident Response Process - ISACA1
* Incident Response: How to Identify and Fix Security Weaknesses

The first thing that the audit manager should do when faced with a situation where only 60% of the audit has been completed and the due date is approaching is to determine where delays have occurred. This can help the audit manager to identify and analyze the root causes of the delays, such as unexpected issues, scope changes, resource constraints, communication problems, etc., and evaluate their impact on the audit objectives, scope, quality, and timeline. Based on this analysis, the audit manager can then decide on the best course of action to address the delays and complete the audit successfully. Assigning additional resources to supplement the audit is a possible option for resolving delays in an audit project, but it is not the first thing that the audit manager should do, as it may not be feasible or effective depending on the availability, cost, and suitability of the additional resources. Escalating to the audit committee is a possible option for communicating delays in an audit project and seeking guidance or support from senior management, but it is not the first thing that the audit manager should do, as it may not be necessary or appropriate depending on the severity and urgency of the delays. Extending the audit deadline is a possible option for accommodating delays in an audit project and ensuring sufficient time for completing the audit tasks and activities, but it is not the first thing that the audit manager should do, as it may not be possible or desirable depending on the contractual obligations, stakeholder expectations, and regulatory requirements.

A business impact analysis (BIA) is a process that identifies and evaluates the potential effects or consequences of disruptions or disasters on an organization's critical business functions or processes. A BIA can help prioritize the recovery of critical functions by assessing their importance and urgency for the organization's operations, objectives, and stakeholders, and determining their recovery time objectives (RTOs), which are the maximum acceptable time for restoring a function after a disruption. A business continuity plan (BCP) testing is a process that verifies and validates the effectiveness and readiness of a BCP, which is a document that outlines the strategies and procedures for ensuring the continuity of critical business functions in the event of a disruption or disaster. A BCP testing does not prioritize the recovery of critical functions, but rather evaluates how well they are recovered according to the BCP. A disaster recovery plan (DRP) testing is a process that verifies and validates the effectiveness and readiness of a DRP, which is a document that outlines the technical and operational steps for restoring the IT systems and infrastructure that support critical business functions in the event of a disruption or disaster. A DRP testing does not prioritize the recovery of critical functions, but rather evaluates how well they are supported by the IT systems and infrastructure according to the DRP. A risk assessment is a process that identifies and analyzes the potential threats and vulnerabilities that could affect an organization's critical business functions or processes. A risk assessment does not prioritize the recovery of critical functions, but rather estimates their likelihood and impact of being disrupted by various risk scenarios.