When malware moves from the delivery stage to the exploitation stage in the cyber kill chain, its objective often shifts to identifying exploitable vulnerabilities within the targeted system. A port scan is a technique used to discover services that are listening on ports within a system. By scanning the system's ports, the malware can identify open ports and the services running on them, providing valuable information about potential entry points for further exploitation. This type of reconnaissance attack is aimed at gathering intelligence on the target system's network services, which can then be reported back to a command and control center for further malicious activity planning.

Port scanning is more relevant than IP range sweeps, packet sniffing, or session hijacking for identifying useful services on a system because it directly targets the discovery of accessible network services and their corresponding ports. While the other methods can also be part of the reconnaissance phase, they serve different purposes: IP range sweeps aim to identify active IP addresses, packet sniffing intercepts data packets to gather information, and session hijacking involves taking over a valid user session. In contrast, port scanning is specifically designed to enumerate services that could be exploited.