An incident response team has been notified of a virus outbreak in a network subnet. The next step should be to focus on limiting the damage by containing the virus and preventing it from spreading further. This may involve isolating the affected systems, disconnecting them from the network, blocking malicious traffic or applying patches or antivirus updates. Verifying that the compromised systems are fully functional, documenting the incident and removing and restoring the affected systems are possible steps that could be taken after limiting the damage. References:
[Incident Response Definition]
[Incident Response Process | ISACA]
[Virus Definition]

Segregation of duties (SoD) is a key internal control that aims to prevent fraud and errors by ensuring that no single individual can perform incompatible or conflicting tasks within a business process. SoD reduces the risk of unauthorized or improper transactions, manipulation of data, or misappropriation of assets.
In the accounts payable department, SoD involves separating the following functions: invoice processing, payment authorization, payment execution, and reconciliation. For example, the person who approves an invoice should not be the same person who issues the payment or reconciles the bank statement.
One of the best ways to ensure appropriate SoD within the accounts payable department is to restrict program functionality according to user security profiles. This means that each user of the accounts payable system should have a unique login and password, and should only have access to the functions that are relevant to their role and responsibilities. For instance, an invoice processor should not be able to approve payments or modify vendor records. This way, the system can enforce SoD and prevent unauthorized or fraudulent activities.
The other options are not as effective as restricting program functionality according to user security profiles.
Restricting access to update programs to accounts payable staff only is a general access control measure, but it does not address the SoD issue within the accounts payable department. Including the creator's user ID as a field in every transaction record created is a useful audit trail feature, but it does not prevent users from performing incompatible functions. Ensuring that audit trails exist for transactions is a detective control that can help identify and investigate any irregularities, but it does not prevent them from occurring in the first place.

Computer performance is the measure of how well a computer system can execute tasks and applications within a given time frame. Computer performance can be affected by various factors, such as hardware specifications, software configuration, network conditions, and user behavior. To analyze computer performance, it is important to use statistical metrics that can quantify the capacity utilization of the system resources, such as CPU, memory, disk, and network. These metrics can help identify the bottlenecks, inefficiencies, and anomalies that may degrade the performance of the system. Examples of such metrics include CPU utilization, memory usage, disk throughput, network bandwidth, and response time.
The other options are not as useful as statistical metrics when analyzing computer performance. An operations report of user dissatisfaction with response time is a subjective measure that may not reflect the actual performance of the system. Tuning of system software to optimize resource usage is a corrective action that can improve performance, but it is not a method of analysis. A report of off-peak utilization and response time is a limited snapshot that may not capture the peak performance or the average performance of the system.
References:
What is Computer Performance?
How to Measure Computer Performance