Mac security software: Necessity and Norton issues?

Absolutely NO! First, there is no reason to ever install or run any 3rd party "cleaning", "optimizing", "speed-up", anti-virus, VPN or security apps on your Mac.  This documents describe what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community and Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support.  

There are no known viruses, i.e. self propagating, for Macs.  There are, however, adware and malware which require the user to install although unwittingly most of the time thru sneaky links, etc.   

Anti Virus developers try to group all types as viruses into their ad campaigns of fear.  They do a poor job of the detecting and isolating the adware and malware.  Since there are no viruses these apps use up a lot of system resources searching for what is non-existent and adversely affect system and app performance.

There is one app, Malwarebytes, which was developed by a long time contributor to these forums and a highly respected member of the computer security community, that is designed solely to seek out adware and known malware and remove it.  The free version is more than adequate for most users.  I have it and it's never found anything on my Mac in 5 years.

Unless you're using a true VPN tunnel, such as between you and your employer's, school's or bank's servers, they provide false security from a privacy standpoint.  Read these two articles: Public VPN's are anything but private and Security Risks: The Dangers of Using Free VPNs (eccu.edu).  

Additionally, a new study ("Apple Offers Apps With Ties to Chinese Military”) is specifically about VPN apps in Apple’s App Store.

Not really. Apple's security is pretty good and the only problem IMO is that it's completely silent and in the background. Additional security apps have the advantage of actually telling you they have done something (allegedly) which might be beneficial for your state of mind but the downsides usually outweigh this benefit. Security and cleaning apps can be responsible for slowing down your Mac at best and messing up its performance to the point of requiring a complete wipe and restore at worse.

TLDR: keep your Mac up to date with security updates and uninstall Norton using the uninstaller that came with it. If it didn't come with an uninstaller come back here and someone will advise how best to get rid of it without leaving any mess behind.

ptlili wrote:

is any additional security software necessary with a mac? norton seems to mess with smooth operation.

One of the better known add-on anti-malware packages for macOS (Avast) was caught and fined for selling personally-identified web browsing and web purchasing data. They were fined for not disclosing the sale in the fine print. Not for actually selling your activities.

Add-on “coffee shop” VPNs have some similar “pinky-promise” security risks, badly solving a problem that hasn’t existed for a decade or so, but badly solving it in a way perfect for collecting personally-identified web browsing data. This as compared with the Apple iCloud+ Private Relay and ODoH support. (And Apple’s Gatekeeper, XProtect, and the signed system volume, among other parts of the defense.)

ptlili wrote:

is any additional security software necessary with a mac?

macOS is built on a secure platform.

see > Apple Platform Security

norton seems to mess with smooth operation.

That happens with most all third-party AV-software.

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