How do you monitor and log unauthorized file access attempts?

Question

Anubhav Kumar · Answer

Monitoring and logging unauthorized file access attempts is crucial for system security and compliance. Here's a breakdown of how you can implement this across different platforms and environments:
1. Windows Systems
Enable Auditing via Group Policy
Run gpedit.msc → Navigate to:
Computer Configuration andgt; Windows Settings andgt; Security Settings andgt; Advanced Audit Policy Configuration andgt; Object AccessEnable:
Audit File SystemSet it to Success and Failure.
Set File/Folder Auditing
Right-click the file/folder → Properties → Security →
Advanced.Go to the Auditing tab → Add.Select the principal (e.g., Everyone or a specific user).Choose which actions to audit (e.g., "Read", "Write", "Delete", "Failed Access").
View Logs
Use Event Viewer → Windows Logs andgt; Security.Look for events with ID 4656, 4663, 
4660, or 4658.
2. Linux/Unix Systems
Auditd (Linux Audit Daemon)
Install and configure auditd:
sudo apt install auditd audispd-plugins
Add File Watch Rules
sudo auditctl -w /path/to/your/file -p rwxa -k unauthorized_access
-w: watch this file-p: permissions (read, write, execute, attribute changes)-k: key to tag events for easier search
View Logs
sudo ausearch -k unauthorized_access
Or check the audit log:
sudo less /var/log/audit/audit.log
Permanent Rules
Add rules to /etc/audit/rules.d/audit.rules.
3. Application-Level Monitoring (Cross-Platform)
If you want to implement monitoring in a custom application, you can:
Wrap File Access in Logic
Check user credentials or permissions before opening a file.Log every failed attempt with timestamp, user, and action.
Example in C#:
try
{
    var user = GetCurrentUser();
    if (!UserHasAccess(user, filePath))
    {
        LogUnauthorizedAttempt(user, filePath);
        throw new UnauthorizedAccessException("Access denied.");
    }
    var fileContent = File.ReadAllText(filePath);
}
catch (UnauthorizedAccessException ex)
{
    logger.LogWarning($"Unauthorized access by {user} to {filePath} at {DateTime.Now}");
}
4. Third-Party Tools
SIEM tools (Splunk, Elastic Stack, etc.): For centralized log collection and real-time alerting.File Integrity Monitoring (FIM) tools: Tripwire, OSSEC, AIDE.
Best Practices
Alert on multiple failed attempts.Combine with intrusion detection/prevention systems (IDS/IPS).Use timestamps, user context, and source IP in logs.Secure your logs to prevent tampering.

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How do you monitor and log unauthorized file access attempts?

Ravi Vishwakarma

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1 Answers

1. Windows Systems

Enable Auditing via Group Policy

Set File/Folder Auditing

View Logs

2. Linux/Unix Systems

Auditd (Linux Audit Daemon)

Add File Watch Rules

View Logs

Permanent Rules

3. Application-Level Monitoring (Cross-Platform)

4. Third-Party Tools

Best Practices

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