What does 'malicious code' typically refer to?

Malicious code refers to software or scripts that are specifically designed to infiltrate, damage, or take unauthorized control of computer systems or networks. The correct choice highlights that this term encompasses various types of harmful software, such as viruses, worms, and Trojan horses. Each of these types functions in a way that can compromise the integrity, confidentiality, and availability of information systems.

For instance, viruses attach themselves to legitimate files and replicate, often spreading to other systems, while worms spread independently across networks. Trojan horses disguise themselves as legitimate software but actually contain hidden malicious functions. These malicious entities can create significant security risks, causing data loss, theft, or other detrimental impacts on system performance and user safety.

The other choices do not accurately represent the concept of malicious code. Enhancements in system performance, network optimization data, or database management files do not have the malicious intent or harmful effect associated with malicious code. Rather, they relate to beneficial functions that maintain or improve the system's overall health and efficiency.