I found a virus with Bitdefender, what is it?

Yes. False positive.

Whether it is Bit Defender or any other anti-virus tool, they have a tendency to flag anything they don't understand, whether it is a valid application component in Apple or third-party software packages, a legitimate operating system file, or adware/malware infestations. Malwarebytes is designed specifically for the latter category and negates the need for any a/v tool.

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

Bit Defender found what it thinks is a virus, but as true Mac viruses do not exist outside of a lab environment, it is likely a false detection. You should not be running anti-virus software on your Mac, as you will likely have more of these false-positive detections when in reality, the a/v tool is either wrong or found non-virus malware.

What you really need is the free trial of Malwarebytes which will scan for adware/malware and remove it. Toss your anti-virus software.

If you only download applications from their original vendor sites, you will eliminate malware baggage that tags along from download aggregation, non-vendor sites.

There are no known Viruses in the wild that self replicate and affect macOS. There are Malware and Adware that does affect macOS and are often times downloaded as part of an Application from Third Party UnTrusted Site and get installed along with the Application.

And for that issue - @VikingOSX has provided a solution

Uninstall BitDefender.