Which of the following is the BEST indicator of the effectiveness of signature-based intrusion detection...

Signature-based intrusion detection systems (IDS) are systems that compare network traffic with predefined patterns of known attacks, called signatures. The effectiveness of signature-based IDS depends on how well they can detect new or unknown attacks that are not in their signature database. Therefore, an increase in the number of detected incidents not previously identified is the best indicator of the effectiveness of signature-based IDS, as it shows that they can recognize novel or modified attacks.