Which term refers to the act of breaking into systems and developing harmful software?

The term that refers to the act of breaking into systems and developing harmful software is hacking. Hacking encompasses a wide range of activities that involve manipulating computer systems, networks, or devices, often with malicious intent. When individuals engage in hacking, they may exploit vulnerabilities to gain unauthorized access to systems and create harmful applications such as viruses, worms, or spyware, which fall under the broader category of malware. This term captures both the act of unauthorized intrusion and the creation of detrimental software, making it the most accurate choice in this context.

Other terms in the question have distinct meanings; for example, software piracy pertains specifically to the unauthorized use or distribution of software rather than the act of breaking into systems. Malware creation refers to specifically developing harmful software, but it doesn't encompass the broader act of gaining unauthorized access to systems. A data breach, meanwhile, involves unauthorized access to data rather than the creation of harmful software or system intrusion itself. Thus, hacking is the most comprehensive and fitting term for the activities described.