Detecting and Containing Ransomware-Induced File Encryption on Enterprise Nextcloud Servers Through File Integrity Monitoring and Automated Incident Response

Enterprise organizations use Nextcloud as a self-hosted file-sharing and collaboration platform for storing and sharing business documents among authorized users.

Because Nextcloud stores files directly on the organization's infrastructure, ransomware activity targeting the Nextcloud data directory can result in large numbers of files being modified or encrypted within a short period.

In this use case, a controlled Nextcloud server environment is deployed on an Ubuntu virtual machine. The Nextcloud application is deployed using Docker, and a separate Kali Linux virtual machine is used as the security-testing environment.

A controlled ransomware-like file-encryption activity is generated against a dedicated laboratory directory associated with the Nextcloud data environment. No real ransomware malware is used. The activity reproduces the file-modification behavior required to validate the defensive workflow.

Wazuh is configured as the primary security monitoring and response platform. Its File Integrity Monitoring (FIM) capability monitors the protected Nextcloud file directories and detects abnormal file modifications.

When a large number of file changes are detected within a short period, Wazuh generates security alerts and triggers an automated response mechanism to contain the affected endpoint or terminate the controlled malicious activity.

The incident is subsequently investigated through Wazuh, the affected files are identified, containment is validated, and the Nextcloud environment is restored to a known-good state.

Nextcloud provides centralized file storage and collaboration functionality. The application depends on the underlying server filesystem to store uploaded and synchronized files.

If an attacker gains execution capability on the Nextcloud server or an authorized endpoint with access to synchronized files, ransomware-like activity can modify a large number of files.

Traditional monitoring may identify individual file modifications as normal application activity because legitimate users and Nextcloud services continuously create, modify, and synchronize files. The security challenge is therefore to distinguish normal file activity from abnormal mass file modification behavior.

The security problem is therefore:

The proposed solution introduces File Integrity Monitoring combined with behavioral alerting and automated incident response.

The attack scenario reproduces the behavior of ransomware by performing controlled encryption-like modifications against laboratory files within the protected Nextcloud data environment. No actual ransomware malware is introduced.

The objective is to determine whether the security monitoring system can identify the rapid modification of multiple protected files and initiate an appropriate response.

The primary security concept is File Integrity Monitoring (FIM) combined with automated incident response.

FIM establishes a baseline of protected files and monitors changes to those files. When unexpected modifications occur, the monitoring system generates security events. For ransomware-like activity, a large number of rapid file modifications can provide an important detection signal.

The secure processing flow is: