The term used for unauthorized software modification is "software tampering." This involves altering a software application's code or functionality without consent from the original creator or owner. Such modifications can lead to vulnerabilities, performance issues, or even malicious behavior, including introducing malware. Software tampering poses significant security risks, as it compromises the integrity and reliability of applications. Organizations must implement strong security measures, including code signing and regular audits, to detect and prevent unauthorized changes, ensuring software remains trustworthy and functional.