Why part of VMDK often survives
Modern ESXi-cryptors optimize for speed: encrypting 50 TB fully takes hours. For an attack that needs to be fast (before detection), operators encrypt only the first megabytes of each VMDK — enough to destroy the VMFS header and make the disk inaccessible via normal mounting. VM internal data (NTFS inside VMDK) often remains intact. Technical recovery exploits this.
Catastrophic ESXi recovery mistakes
- 1.Try fix-vmfs on original datastore. ESXi repair commands try to rewrite metadata. Running on partially encrypted datastore destroys what was still readable.
- 2.Delete encrypted VMDKs thinking they 'just clutter'. Even encrypted, internal content may be extractable. Deletion is irreversible.
- 3.Restore VM in old datastore. Compromised datastore has persistence. Use clean storage.
- 4.Ignore vCenter logs post-incident. vCenter logs show who logged in, when, from what IP. Critical for forensics and to avoid reinfection.
Recovery flow in 5 steps
- 1
Snapshot entire datastore BEFORE any action
Connect datastore storage in isolated read-only environment or create LUN snapshot on SAN. Always work on copy, never on original. Encrypted header may be unique — losing it = no attempt possible.
- 2
Identify VMDK boundaries in datastore
Without functional VMFS header, manual parsing with tools like UFS Explorer Professional, R-Studio or DMDE. Each VMDK file starts with magic number and is aligned at 1 MB blocks.
- 3
Extract raw content of identified VMDKs
Even without normal mounting, professional tools read raw content. Result: dd image of internal virtual disk (usually NTFS, ext4 or XFS for Linux VMs).
- 4
Recover files inside the filesystem
dd image from step 3 can be mounted with testdisk, photorec or forensic tools. Internal NTFS often intact. SQL Server database, application files, medical records extractable.
- 5
Rebuild VMs in new environment
Don't restore on compromised infrastructure. Provision new vCenter, clean ESXi, create new VMs and migrate recovered files. Hardening simultaneously (Windows hardening post steps).
FAQ
What is the success rate of ESXi recovery post-ransomware?
Varies by case. With intact datastore snapshot + partial encryption (header only): 70-90% of internal data recoverable. Full encryption or compromised physical storage: 20-40%. Without backup, technical datastore recovery is the only alternative before considering payment.
How long does it take?
10 TB datastore: 3-7 business days. 50 TB: 10-20 business days. Time depends on internal filesystem complexity and VM quantity.
Can I do it myself without a lab?
Technically yes with UFS Explorer Professional (~US$ 1,500 license), but learning curve is high. Mistakes destroy data. For critical corporate case, specialized lab is cheaper considering error risk.
What if physical SAN was also attacked?
More complex case. If SAN has pre-incident array-level snapshot (NetApp, Pure, Dell EMC) intact, can be restored. Without snapshot, physical SAN recovery is necessary.
Can Veeam backup restore post-attack?
If backup was immutable (Hardened Repository / Object Lock) and not reached by attacker: yes, restore in new environment. If mutable backup was also encrypted: need to recover storage.
ESXi datastore encrypted by ransomware?
VMware specialists. Preservation snapshot within 6h. Documented chain of custody.