Veeam Backups

Data Recovery from a Ransomware-Encrypted Veeam File Share Backup

This real-life case illustrates how a sophisticated attack can bypass even the most robust protections, but also how expert intervention can make it possible to recover most of the data. What follows is the story of a race against time.

Imagine this: it is 10 p.m. on a Friday evening, and a company based in Seoul, a leader in the human resources sector, discovers in horror that all of its critical files have been encrypted by ransomware. These data, stored on a centralised NAS, are vital for production teams and administrative departments. Among them are Veeam NAS backup files, which were supposed to protect the company against this type of attack. Yet the cybercriminals managed to access the NAS with administrator privileges, encrypting not only business data but also the backups themselves.

Context: a critical infrastructure under attack

A centralised NAS at the heart of the business

The company’s storage relies on a NAS (Network Attached Storage) centralising more than 2 TB of data, representing over 650,000 files. This storage supports both day-to-day operations and strategic archives. To secure these data, the company had implemented Veeam NAS Backup, a solution renowned for its ability to handle millions of files without performance degradation, while also providing protection against accidental deletions and ransomware through a versioning system.

Veeam NAS Backup is optimised for NFS and SMB shares and provides fine-grained file-level recovery. However, even the best solutions have their limits: if an attacker gains administrator privileges on the NAS, they can encrypt all data, including the backups.

The attack: Friday, 15 August 2025 at 10 p.m.

Here is what happened: The cybercriminals exploited a vulnerability to gain access to the NAS with administrator privileges. As a result, all files, including the Veeam backups, were encrypted. The .vblob, .vindex, and .vslice extensions – essential to the operation of Veeam backups – were renamed and rendered unreadable.

Faced with this situation, the company found itself at a dead end:

Inability to access data: the files were encrypted and their names altered.
Operational urgency: every hour of downtime threatened business continuity.
Uncertainty over recovery: the backups themselves were compromised.

The challenge: recovering encrypted backups

Understanding the Veeam NAS Backup architecture

Before taking action, it is crucial to understand the structure of Veeam NAS Backup files:

.vblob: these files contain the raw data captured from NAS share backups.
.vindex: these are binary metadata files describing the names and versions of the backed-up files.
.vslice: these files describe how data is allocated within the .vblob files.

Without this metadata, restoration is nearly impossible. Nevertheless, the technical teams at Recoveo (our company) decided to take on the challenge.

A two-fold approach

To maximise the chances of success, two teams were mobilised:

The “File Structure” team: responsible for rebuilding the folder and file hierarchy.

2.The “Data” team: focused on extracting and recovering the raw data.

The solution: a tailored recovery process

Step 1: Analysis of the file structure

The first step involves carrying out an in-depth analysis of the encrypted file structure. Using hexadecimal analysis and reverse engineering tools, the engineers identify recurring patterns within the .vblob, .vindex, and .vslice files. This analysis makes it possible to understand how the data were organised prior to encryption.

The .vindex files contain specific headers which, once decoded, reveal information about file names and their hierarchy.

Step 2: Development of a proprietary extraction tool

As no generic solution were proven effective, our engineers developed a bespoke tool capable of:

Parsing metadata: extracting information from the .vindex and .vslice files despite their encryption.
Rebuilding the directory structure: restoring the original folder hierarchy.
Extracting raw data: recovering the contents of the .vblob files and linking them back to their original names.

Step 3: Restoration testing

Before launching a large-scale extraction, tests were carried out on critical files (contracts, HR databases, administrative documents). These tests validated:

Data integrity: the restored files were tested to ensure they were usable and intact.
Directory structure consistency: folders and subfolders were correctly rebuilt. The client provided a complete list of their original directory structure, allowing us to compare it with the recovered result.

Step 4: Extraction and validation

Once the tool was finalised, the extraction process was launched. Files were recovered in batches, with systematic integrity checks. A detailed list of restored files was generated, enabling the company to validate the completeness of the recovered data.

Results: 93% of data successfully recovered in under one week

A success beyond expectations

Contrary to the initial forecasts, 93% of the data from the Veeam NAS Backup was recovered. This exceptional recovery rate can be explained by:

The robustness of the developed tool: capable of bypassing metadata encryption.
Information redundancy: the .vblob files contained sufficient redundancy to reconstruct a large portion of the data.
The expertise of the teams: the combination of skills in cybersecurity, software development, and data management proved decisive.

Client testimonial

“With Recoveo, we found a solution to recover our data from our Veeam NAS Backup. The restoration was nearly complete, and we were able to resume operations in less than a week. This intervention saved years of work and prevented a major crisis for our company.” — Yu-jun Chung, IT Expert

Lesson learned from this crisis

The importance of an expert partner

When facing a ransomware attack, every minute counts. Turning to data recovery experts can make the difference between a fast return to operations and irreversible data loss.

Conclusion: a victory against ransomware

This story shows that a ransomware attack, however devastating, can be resolved successfully. Thanks to advanced technical analysis, a bespoke tool and close collaboration with the client, it is possible to recover a large portion of the data. If your organisation is facing a similar situation, please contact us now. Our teams are ready to support you in minimising its impact and restoring your critical data.