A system specializing in the monitoring and analysis of network traffic to identify and potentially alert on malicious activities is the correct choice for real-time analysis of security threats on a network. Signature-based detection would refer to the specific method of detecting known patterns or signatures of malicious software, but does not define the system itself. While encryption services are crucial for securing data in transit, they do not provide the functionality of analyzing traffic for threats. Patch management is necessary to ensure systems are up-to-date but does not involve network traffic analysis.