Final answer:
The program that detects when another computer is attempting to scan a disk or access a computer is an Intrusion Detection System (IDS). This system is distinct from adware, packet-filtering firewalls, and general network security systems, with the IDS specializing in the detection of potential unauthorized access or policy violations.
Step-by-step explanation:
A computer program that senses when another computer is attempting to scan a disk or access a computer is known as a(n) Intrusion Detection System (IDS). An IDS can monitor network or system activities for malicious activities or policy violations and can send reports to a management station.
It differs from a packet-filtering firewall, which controls access to a network by analyzing incoming and outgoing packets and passing or blocking them based on the source and destination Internet Protocol (IP) addresses, protocols, ports, and other content.
Adware, on the other hand, is an unwanted software designed to throw advertisements up on your screen, most often within a web browser. Lastly, a network security system is a broader term that encompasses tools, devices, and processes that monitor and protect the entire network from a range of potential threats but is not specific to the activity of scanning or unauthorized access detection.
Therefore, the correct answer to the original question is: A) intrusion detection system.