The scenario described is indicative of a port scanning attack. Port scanning is a method used by attackers to discover open ports on network devices. A single SYN packet sent to each port is a technique known as SYN scanning or half-open scanning, where the attacker sends a SYN message (as if they are going to initiate a TCP connection) to every port on the server, looking for positive responses which indicate an open port. This type of scanning is less intrusive and harder to detect because it never completes the TCP three-way handshake1.
References: Cisco community resources on Denial of Service (DoS) attacks

Social engineering techniques often involve manipulating individuals into divulging confidential information or performing actions that compromise security. Phishing involves sending fraudulent messages (often emails) that appear to be from reputable sources with the goal of stealing sensitive data or installing malware.
Pharming redirects the traffic of a legitimate website to another fraudulent website without the user's knowledge, aiming to collect the user's credentials. References := Cisco Cybersecurity Source Documents

Statistical detection involves collecting data over time to define what is considered normal behavior or legitimate data for users or systems. It then uses statistical analysis to identify abnormal behavior that could indicate a security incident. Rule-based detection uses predefined rules or patterns that are based on known threats or vulnerabilities - it operates on an IF/THEN basis where if certain conditions are met then an alert is triggered. References := Cisco Cybersecurity Operations Fundamentals