Bitdefender Antivirus continuously scanning active threats(trojan virus) after opening a website.

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. 

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.

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

Any Third Party Applications that will interfere with the normal operation of the OS, alter, modify, remove or delete or attempt to do so is an invitation for disaster and comprising the Operating System

Any of the below should be removed as per Developers Instructions 

This will include BitDefender , 

There has been sufficient advise offered for the User 9 You ) to make an informed and educated choice what the next course of action is required.

The suggestions have been put forth on a volunteer basis, in good faith and in the best interests of the computer.

https://www.bitdefender.com/consumer/support/answer/1784/

Personally - after using their specific Instructions and to make sure all the Bits & Pieces are truly totally removed >>

Download the Application Etrecheck directly from a well Respected ASC Contributor. And Safe to use.

The application is free or paid from added features. 

Run the application with Full Disc Access ( Security & Privacy - Full Disc Access ).

It will take a Snap Shot -  both the hardware and software.

 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 )

We can have a look at the report for possible issues and may have possible suggestions to resolve the issues.

You don't need an AV product as macOS has its own.

All these type "helper" apps carry a high likelihood to disrupt OS processes and should be uninstalled ... all of them.

You need to follow the developer's uninstall instructions precisely to get rid of all the pieces and parts.

it's not uncommon for Mac OS's built in AV and 3rd party to conflict and behave erratically. "Virus's" management on MacOS can be very different than what you might be used to on windows. the biggest one I notice IMHO is the coordination between Apple and these AV developers; there is none.

Thank you for taking the suggestion and issuing the Etrecheck Report

Specific to BitDefender - elements are still present in this report

EtreCheckPro version: 6.6.1 (66021)

Report generated: 2022-06-22 21:55:44

Q -  No Time Machine backup - Time Machine backup not found.

A - Any Personal Data that is worth keeping deserves protection. Under this setup - all personal Data appears to be expendable.

Q - 2022-06-18 Bitdefender Virus Scanner (3.17)

Q - 2022-06-20 19:12:19 BitdefenderVirusScanner.app High CPU Use (3 times)

    Executable: /Applications/BitdefenderVirusScanner.app

FWIW, I would not have it installed on my Macs. However, since you do, contact Bitdefender support.

https://www.bitdefender.com/consumer/support/