security software will not update

What security software? Please read Writing an effective Apple Support Communities question. We are here to help. We are all users. We are not mind-readers nor clairvoyants. We only know what you write down and tell us. Be specific and thorough. Include your hardware information and installed version of macOS.

FYI: These are user-only forums. You are not speaking to Apple. if you need to speak with Apple Support, then contact product and tech support:  Contacting Apple for support and service including international calling numbers.

Thank you for your understanding and support.



If you are on macOS High Sierra and looking for the recent Security Update you can find the standalone version here,

https://support.apple.com/kb/DL2026?viewlocale=en_US&locale=en_US

Once downloaded double-click to install.

It is worth remembering to connect your mac to your router using a cable rather than rely on Wifi when downloading

System and Security Updates.