Which of the following is NOT considered malicious code?

The reason executables are not considered malicious code can be attributed to their nature and functionality. An executable is a type of file that is designed to carry out a particular set of instructions on a computer system, allowing programs to run and perform tasks. This includes everything from operating system functions to applications that assist in productivity.

While some executables can indeed be malicious, the term itself encompasses both benign and harmful software. In contrast, viruses, worms, and spyware are all specifically designed with malicious intent to compromise system security, steal information, or cause harm. Viruses attach themselves to legitimate programs, worms replicate across networks, and spyware secretly monitors user activity to gather sensitive information. Thus, not all executables possess malicious intent, making them distinct from the other options listed.