My Internet slowed down after installing update 12.6.8

Since some millions of users don't see internet slowdowns after that update, it is most likely something local in your setup. First steps could include:

• rebooting your modem
• rebooting your router
• turning WiFi on and off in your laptop

If you are using any third party antivirus, security software, internet traffic monitoring software, VPN, Mac "cleaner" software ... those tools have been known to work ok with older versions of the MacOS but not work well after an update due to being incompatible with the updated MacOS. Usually an update to the latest version of the third party software resolves this. Better would be to completely uninstall such software (if you are using any) as they are not needed and sometimes cause harm.

I might be that you need to update it or it might be that it does not work well with these later versions of MacOS.

In any case, Bitdefender with its built in VPN and other intrusive methods of monitoring everything on your Mac is a candidate to UNINSTALL and see if that makes any difference. If not difference, you can simply reinstall. Turning it off but leaving it installed is not the same, it is still there. Anything with VPN almost certainly slows down the internet. My employer requires VPN and when I am using it, it slows things by 50% or more. The amount of slowness can vary with different versions of the MacOS.

Programs like Bitdefender are not needed. macOS has built in protections that work much better.

If you want to keep it anyway, I suggest you completely uninstall it and see if that has any effect. If not, you can reinstall but I would not.

Etrecheck

Download the Application Etrecheck directly from the Developer.

This is a Diagnostic Tool that makes no changes to the computer.

It makes a coherent and readable inventory of both the Hardware and Software used on the computer

The application is free or paid from added features. 

The Report will Not Reveal Any Personal Information. 

Post back the Full Report - copy and paste - >>>> using the Additional Text Icon ( 3rd Icon to last ) <<<<

https://etrecheck.com/

Welcome

We are just interested.

Has the Internet Slowdown issue been fixed since BitDefender has been removed ?

Just to add to @steve626 good advise

There are no known Windows-like Viruses in the wild that self replicate and affect macOS, because of the underling UNIX  Foundation and Permission Limitation. 

Starting in macOS 11 Big Sur and above. 

The Operating System resides in a Sealed and Read Only Volume that can not be opened by the User nor by Third Party Applications.

The only Entity that can open and modify or alter this Volume is Apple.

That would occur when a update or UpGrade is performed.

The Only thing this Antivirus software is protecting is the Bank Account of the Developers and for zero return to the User aside from the problems this software creates.

AntiVirus Developers purposefully Market their product to create a “ Fear Factor “. In so doing, creating a False Need for their Product.

The The Built in Security  is all that is required to protect the computer.

Any of the below should be removed as per Developers Instructions 

This will include BitDefender , 

Read some of the posting and arrive at your own conclusions.

We have five Macs ... three on Ventura and two on Monterey.

All five of them, years 2015 to 2020, have never experienced any slowdowns of the type you describe. And that represents maybe 25-30 upgrades total. More really considering all the app updates we get to have.

Just because it happens on your system is not indicative that it happens on all systems.

Our internet plan provides us with a 600 MBps plan and undoubtedly that is a point in enabling fast and reliable upgrades.

I suggest you talk to your ISP and determine if your plan is as fast and reliable as you think it is.

++1 on both replies

Welcome.

It usually a good idea to investigate All possible issues before arriving a certain conclusions