Protecting Your .NET Website from Suspicious 404 Spikes: Signs of an Attack

🚨 Investigating Unexpected Downtime and Security Anomalies

In a recent system inspection, our team encountered a sudden downtime that coincided with several alarming patterns most notably, a surge of over 10,000 404 errors targeting WordPress and PHP paths. Given that our platform is built entirely with .NET, these findings strongly suggest a potential hacking attempt or bot-driven reconnaissance attack.

In this article, we’ll walk through our observations, provide actionable recommendations and explain how integrating Cloudflare and other .NET-native security measures can significantly harden your application.

🔍 Key Observations

Excessive 404 Errors:
More than 10K 404 responses were logged in a short timeframe. Most were targeting endpoints like /wp-login.php, /xmlrpc.php and other common WordPress paths none of which exist in a .NET environment.
Suspicious Traffic Patterns:
Logs showed aggressive, automated access attempts, likely coming from bots or malicious actors scanning for vulnerable targets.
Performance Impact:
While our application itself remained unaffected functionally, the sheer volume of requests led to downstream issues such as timeouts and slowed responses, suggesting resource strain from invalid traffic.

🛡️ Recommended Security Measures

1. Perform a Security Audit

Review all 404-generating requests and classify them by IP, path, user agent and request frequency.
Look for repetitive, scripted patterns indicating brute-force or vulnerability scanning tools.

2. Enable Custom Error Handling

Implement custom 404 error pages in your .NET application (via web.config or middleware) that do not leak system details.
Log all 404s with metadata for forensic review but avoid echoing full URLs or technical stack information to users.

3. Block Malicious Traffic

Identify abusive IPs from logs and block them at the server or application level.
Use IIS IP Restrictions, middleware or .NET security libraries to automate basic request filtering.

4. Introduce Rate Limiting

Add middleware-based request throttling to block or delay repetitive requests from the same source.
Apply stricter limits on suspicious paths like /php, /wp-*, etc., since they shouldn’t be accessed at all in a .NET context.

5. Cloudflare Integration

Cloudflare provides a comprehensive front line of defense that complements your .NET backend:

Web Application Firewall (WAF): Block attacks before they reach your server.
DDoS Protection: Automatically mitigate volumetric attacks with minimal configuration.
Bot Management: Detect and neutralize malicious bot traffic targeting your site.
Rate Limiting: Configure custom rules to restrict suspicious high-frequency access.
CDN & Caching: Improve load time and reduce server strain during high traffic.

📊 Monitoring & Alerting

To catch future incidents early:

Set up Azure Application Insights or Log Analytics to monitor request trends and alert you to anomalies.
Trigger alerts for spikes in 404s, requests to unknown paths or unexpected increases in latency or server load.

🔁 Routine Maintenance Recommendations

Review and update URLs: Ensure all internal and external links are valid to reduce noise in 404 logs.
Redirect where appropriate: Use 301 redirects in IIS or app routing logic to guide users from deprecated URLs.
Security Patch Management: Keep all .NET dependencies and server components up to date.

✅ Conclusion

404 spikes targeting non-existent WordPress paths in a .NET environment are not just noise they’re signals of potential probing or attack attempts. By conducting proper analysis, implementing structured mitigation strategies and leveraging Cloudflare's protection stack, you can drastically improve the resilience and security posture of your application.

Don’t wait until the next incident act proactively, monitor continuously and secure defensively.