Best macOS for iMac (Retina 4K, 21.5-inch, Late 2015

CliveLJ wrote:

Thank you Owl-53,

So, what does this mean for Security on my iMac i.e. the OS is outdated and not secure? I question, is it secure for banking, share trading and any subscription services - is my data secure? Can the security be achieved using this Monterey macOS by way of an anti-virus?

I'm not keen to incur the huge expense of replacing my current working iMac, but what can be effectively done to keep the machine working effectively, securely?

The most important point for internet security (online banking, internet services, etc) is to use a reputable web browser that provides ongoing internet data security updates, preferably one with responsible data management. Bonus points for Adblocking. Firefox requires Catalina or newer. Vivaldi requires Big Sur or newer. Brave requires Monterey or newer.

You still have options for secure internet use, but your options will dwindle each year you are unable to update to a newer version of MacOS.

The second most important point is to only install software from a trusted source. Social engineering trojans are the biggest Mac threat. It is a lot easier to convince a user to voluntarily install FreeMoneySoftware or whatever that instead does a BadThing than it is to write a worm or virus that can get past Gatekeeper.

CliveLJ wrote:

Thank you Owl-53,

So, what does this mean for Security on my iMac i.e. the OS is outdated and not secure? I question, is it secure for banking, share trading and any subscription services - is my data secure? Can the security be achieved using this Monterey macOS by way of an anti-virus?

I'm not keen to incur the huge expense of replacing my current working iMac, but what can be effectively done to keep the machine working effectively, securely?

You are welcome

That’s a very reasonable concern — especially if you’re using your iMac for banking and investments.

Is macOS Monterey “not secure”?

If you’re running macOS Monterey (released 2021), the key question is:

Is it still receiving security updates from Apple?

Apple typically provides security updates for The current macOS 26 Tahoe  and the previous two versions macOS 15 Sequoia and macOS 14 Sonoma 

Once a macOS version falls outside that window, it no longer receives security patches, even if new vulnerabilities are discovered.

Will antivirus make Monterey secure?

Short answer: No 

Windows-like viruses that self-replicate and affect macOS don’t exist because of the underlying UNIX Foundation and permission limitations.

The macOS operating system resides in a sealed and read-only volume that can’t be opened by users or third-party applications.

Mac app security enhancements are sufficient to protect computers from malware.

Adware and Malware can affect computers and are often downloaded from “shady” websites or developers who inject them into downloads.

Source: User tip from @Kurt Lang

https://discussions.apple.com/docs/DOC-250008855

What can you realistically do without replacing the iMac?

That is a question only you can answer 

You do need to know, Apple has been transiting away form Intel based computer since about 2020 with the introduction of their first Apple Silicon Computer 

Fast forwards 6 years to 2026 and that transition is complete in that once macOS 27 is released this Fall 2026

Only Apple Silicon computers will qualify. Intel machines will only be able to upGrade to a maximum of macOS 26 Tahoe 

If your plans for the near future are to stay using Apple Computers and Recent Versions macOS 

You may consider you options carefully 

CliveLJ wrote:

• What is the best OS for my iMac (Retina 4K, 21.5-inch, Late 2015), configured as follows:

Display

21.5-inch (diagonal) Retina 4K display with IPS technology

• 4096-by-2304 resolution with support for millions of colors

Processor

• 3.3GHz quad-core Intel Core i7 (Turbo Boost up to 3.8GHz)

• Memory

16GB of 1867MHz LPDDR3 onboard memory

• Storage1

2TB Fusion Drive

• Graphics

Intel Iris Pro Graphics 6200

It's currently using macOS Monterey 12.7.6

macOS 12.7.6 is the last version of macOS this Computer Qualifies to run

macOS 13 Ventura is compatible with these computers

iMac