A. To prevent unauthorized installations, ensure that your system's security settings are configured to block installations from unknown sources. You can do this by going to your system settings, navigating to 'Security' or 'Privacy', and enabling options that restrict installations from unverified sources.
B. Regularly check your installed programs and remove any that you do not recognize or did not install intentionally. You can do this by going to 'Control Panel' > 'Programs' > 'Programs and Features' on Windows, or 'Applications' on macOS.