Which statement about Cisco IPS signatures is true?
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A. B. C. D.D.
The correct answer is D. "It is recommended to retire a signature not being used to enhance the sensor performance."
Explanation:
Cisco Intrusion Prevention System (IPS) signatures are predefined rules or patterns that identify specific attacks or activities on a network. When an IPS signature detects a match with the network traffic, it generates an alert or takes appropriate action based on the configuration.
Let's go through the options one by one:
A. All of the built-in signatures are enabled by default. This statement is not true. By default, only a subset of signatures are enabled, and it is up to the administrator to enable the rest based on their requirements.
B. Tuned signatures are built-in signatures whose parameters cannot be adjusted. This statement is not true. Tuned signatures are built-in signatures whose parameters can be adjusted to match the specific needs of the network environment.
C. Once the signature is removed from the sensing engine it cannot be restored. This statement is not entirely true. It is possible to restore a signature that has been removed from the sensing engine, but it may require additional configuration steps.
D. It is recommended to retire a signature not being used to enhance the sensor performance. This statement is true. Removing unused signatures can improve the IPS sensor's performance by reducing the processing load on the sensor. It also reduces the number of false positives generated by the system. Retiring unused signatures can also reduce the time needed for signature updates and maintenance.
In summary, the best answer is D. Retiring unused signatures is a recommended practice that can improve the performance and efficiency of an IPS sensor.