How can I tell if someone is accessing my iMac?

this apple support article will give you suggestions on what to look for:

Checklist: If you want to see if anyone else has access to your device or accounts - Apple Support

Hey there!

I understand your concern. First off, Mac’s are the most secure devices in the world. I truly believe that. The big question is, did you provide these people any personal information? (Account or network passwords, social security numbers, banking information)?

If not, then you should be fine.

Can you say what, if any software was installed for them to access your Mac? Of course with permission they can, but access always requires your approval, depending on the access that was allowed.

If you didn’t provide any personal information, I’d focus on any, of any, third party software that was installed on your Mac.

First, starting in Safe Mode is a good step:

Start up your Mac in safe mode:

https://support.apple.com/guide/mac-help/start-up-your-mac-in-safe-mode-mh21245/mac

While there, I’d open:

System Preferences > Users and Groups > Login Items.

These items are set there to open when you log in.

If you don’t recognize something there, you can remove it by highlighting it, and pressing the “-“ below.

Then I would restart your Mac normally.

Other than that, you should be fine, depending on what (If anything) was installed, there are other settings and places to look for malicious software, just let me know.

99% of these people just try to scare others, to pay them to fix the “problem” even when there is no problem, and they tell you there is one.

Otherwise, they do the same to try to pull your accounts information from you.

So 99% of the time, especially on Apple products, You never have to worry. But let me know exactly what, if anything, was installed.

Otherwise, if you did provide any personal information, that’s what’s important. If bank information, contact your financial institution. If any account information, change your passwords and update security to Two Factor Authentication:

Two-factor authentication for Apple ID:

https://support.apple.com/en-us/HT204915

Otherwise, if you did t install anything or give any personal information, these articles may help:

Recognize and avoid phishing messages, phony support calls, and other scams:

https://support.apple.com/en-us/HT204759

Identify legitimate emails from the App Store or iTunes Store:

https://support.apple.com/en-us/HT201679

It’s unfortunate what’s going on nowadays with all these scammers, agree 100%, and it does make me upset. So staying up to date on account and device security and knowing what’s out there is number one. One thing I know, if I want a device or account to be secure, there’s no other company I trust more than Apple. Sounds corny, but I’ve seen the alternatives.

Good luck! Let me know if you have any questions, and if you still are concerned, give them a call:

Contact Apple for support and service:

https://support.apple.com/en-us/HT201232

Hey again!

Is this Norton in the screen shot you sent?

I would probably uninstall that, as said.

I’d then probably download Malware Bytes For Mac:

https://www.malwarebytes.com/mac/

(You can download and run the free version if you want).

Restart once that scam is finished.

Then I’d create a new network location:

https://support.apple.com/en-us/HT202480

As said one the article by Locations, click on the drop down menu > Edit Locations > “+” > Give it a name, whatever you want it to be > Done > Apply (On the bottom right, this will disconnect your connection just for a few seconds).

Once you’re connected again, I’d open and run Malware Bytes again, if any threats, quarantine and restart again.

If you’ve already removed the login items, and any Apps or network interfaces or Extensions that may have been installed on your Mac, this should make sure it’s fine.

Hope that helps!

Further - to see who has Logged into this computer >> Open Terminal >> type the word " last " without quotation marks. It will list ALL persons logging into the computer by date and time.

Contributor @DiZoE has proved Very Good and complete guidance and things to look out for. Nothing more to add Except you mentioned Installing " Norton anti virus " This is One of the Worst of the Worst AntiVirus for Mac Computer. Actually, an AntiVirus Software on a Mac is useless as there are not Known Viruses in the wild affecting macOS. It is strongly suggested removing this Cra*ware Only via The Developers Instructions. Do Not Drag and Drop to Trash as portions of the application my be still lurking on the computer.

Are there any AntiVirus, Disk Cleaner, Optimizers, Defrag, VPNs etc installed which should be removed as per Developers Instructions. They are useless, unneeded, cause havoc , may corrupt the OS and interfere with the normal operation of the OS. The Built-in Security of Big Sur is all that is required.

Norton AntiVirus for Mac - have to Strongly Suggest - Get it Off the computer asap. It is notorious for really messing up the OS to the Point you will have to Reinstall the OS from ground up. As for It Norton AntiVirus picking up Virus or some such things - There are No Known Virus in the wild that affect macOS. So the Claim by such companies is Just Fear Tactic to drive revenue.

Don't believe me - read this thread on BitDefender - same type of product, Or this One specific to Norton Av

Great find, frog! 👍

thanks.

@ jefferythe frog Great work once again - Got that one bookmarked

Welcome and Thank you too :-)

Am 68 Retired and learning new stuff daily. Slow and easy.