Control Flow Integrity (CFI) is a security technique used in computer systems to ensure that a program executes only in a predetermined manner. It prevents attackers from diverting the flow of a program to malicious code, which can lead to vulnerabilities and exploits. By validating the control flow of a program at runtime, CFI helps maintain the intended execution paths. CFI works by creating a map of legitimate control flow paths during the program's compilation. During execution, the system checks that the program follows these paths, blocking any unauthorized changes. This approach enhances the overall security of software applications and systems.