Does Catalina OS along with Norton anti-virus onMacbook Air protect from latest security threat?

Norton does absolutely nothing useful. Nor does any other typical AV software. Get rid of it.

Apply the recent update for Catalina. That's all you need to do.

Norton will slow down your computer and is known for causing other problems. Use Norton's uninstaller app to completely remove all of their app.

See this great article written by a respected forum contributor on safe computing practices:

Effective defenses against malware and other threats - Apple Community

Safe computing practices combined with the security features of macOS should be more than sufficient to prevent most problems to keep your computer and devices working smoothly and keeping yourself safe.