Deep packet inspection (DPI) analyzes the data part (and possibly also the header) of a packet as it passes an inspection point, searching for protocol non-compliance, viruses, spam, intrusions, or defined criteria to decide whether the packet may pass or if it needs to be routed to a different destination. Stateful inspection, on the other hand, tracks the state of active connections and determines which network packets to allow through the firewall. While stateful inspection tracks the state of connections (Layer 4 - transport layer), DPI goes further by examining the payload of the packet (Layer 7 - application layer).
Cisco's official documentation and cybersecurity courses would explain the differences between deep packet inspection and stateful inspection, including their respective layers of operation.

In this scenario, the threat actor refers to the individuals or entities responsible for the attack that resulted in a breach of assets and sensitive information. The receptionist received a threatening call but did not take action, leading to an actual breach within 48 hours. Reference: The explanation is inferred from general cybersecurity knowledge as specific details are not provided in the Cisco Cybersecurity documents linked.

Cyber attribution identifies the threat actors of an attack in an investigation. Threat actors are the individuals, groups, organizations, or states that are responsible for conducting or sponsoring a cyberattack. Threat actors can have different motives, such as financial gain, espionage, sabotage, activism, or warfare. Cyber attribution can help investigators to determine the identity, location, affiliation, and motivation of the threat actors, as well as to hold them accountable and impose sanctions or legal actions. References := Understanding Cisco Cybersecurity Operations Fundamentals (CBROPS) v1.0, Module 5: Security Policies and Procedures, Lesson
5.2: Incident Response, Topic 5.2.3: Cyber Attribution, page 5-14.

Section: Security Monitoring