Trying to backup to my NAS system via time-machine on a MAC

I am trying to backup my hard drive to my external NAS system via Time-machine on my Mac. Bit-defender keeps blocking it and telling me

An unauthorized app attempted to access your backups.

App: /System/Library/CoreServices/backupd.bundle/Contents/Resources/backupd

We blocked the app to prevent it from altering the content of your backups.

Can anyone tell me how i can unblock this?

Thank you