Deep packet inspection (DPI) is a sophisticated method of examining the content of data packets as they pass through a network checkpoint, including both the header and the data payload. DPI is typically performed at the application layer of the Open Systems Interconnection (OSI) model. This allows the inspection process to evaluate the actual content of the packets, not just the header information, enabling the identification of various types of threats and the enforcement of network policies1.

Behavior-based detection monitors the behavior of programs in real-time. If a piece of software acts similarly to known malware after it's been executed, behavior-based detection can stop it in its tracks. Signature-based detection involves searching for known patterns of data within executable code; if a pattern matches a
"signature" in the system's database that is considered malicious. References: Cisco Cybersecurity Operations Fundamentals

HIDS is capable of monitoring the internals of a computing system as well as the network packets on its network interfaces. Host-based firewall is a piece of software running on a single Host that can restrict incoming and outgoing Network activity for that host only.

According to the NIST SP 800-61 incident handling process, the SOC team should first isolate the affected endpoints to prevent further spread of the attack and take disk images for analysis (A). This helps in preserving evidence for a thorough investigation. The next step would be to block the connection to the C&C server on the perimeter next-generation firewall , which helps to cut off the communication between the compromised endpoint and the attacker's server, thereby mitigating the threat123.
References: The answers are based on the guidelines provided in the NIST SP 800-61 Computer Security Incident Handling Guide, which outlines the steps for incident handling, including detection, analysis, containment, eradication, recovery, and post-incident activities