Which of the following technologies is used to detect unauthorized attempts to access and manipulate computer systems locally or through the Internet or an intranet?

An IDS continuously analyzes network traffic and system events against known attack signatures or behavioral baselines to detect unauthorized access attempts and manipulations, whether they originate locally, from an intranet, or from the Internet. It is the control explicitly designed for detection and alerting rather than prevention or segmentation, which directly matches the question's requirement.

A DMZ is a network architecture segment that isolates public-facing servers from the internal network, providing structural separation but not active detection of intrusion attempts.

Packet filtering evaluates packet headers against static rules to allow or deny traffic but does not analyze behavioral patterns or signatures associated with intrusion attempts.

A firewall enforces access control policies based on predefined rules but does not inspect traffic deeply enough to detect and alert on intrusion patterns beyond those rules.