I have worked with environment were hackers encrypted customers servers with Windows build-in bitlocker and hide key
VM Backups taken as VmWare level: So all backup data also encrypted.
Looks this is quite rising hacking method

I just tested how Veeam 12.1.1 detect about Bitlocker encrypted VM:
1. Full backup and several increment took from test vm.
-> last increment shows about 800MB read
2. Enable Bitlocker and wait full disk encrypted
3. New incremental backup
-> Veeam shows now full 90GB boot disk read
No any warning about disk changed to encrypted volue/Disk
Also next mail about Malware Detection report shows 0
Veeam ENT+ used
I opened a support case and got an answer:
BitLocker is a legitimate encryption tool developed by Microsoft to protect data stored on Windows computers. It's intended to enhance security by encrypting entire disk volumes, preventing unauthorized access to data in case the device falls into the wrong hands. It's a proactive security measure rather than a malicious attack like ransomware. Thus, it's expected that Veeam does not identify it as ransomware.
From customer side, they sees disks as unawailable enrypted disks, no matter how they are encrypted !!!!