If you're seeing ELMAH error logs with messages like:

System.Web.HttpException: A public action method 'muieblackcat' was not found on controller...

You're witnessing a common scan pattern used by malicious bots probing for vulnerabilities in ASP.NET MVC applications. This isn't a random attempt - it's part of a systematic scan for known security holes.

The term "muieblackcat" appears to be a fingerprint of specific vulnerability scanning tools or botnets targeting ASP.NET applications. These scans typically:

• Check for outdated versions of popular CMS platforms
• Probe for unsecured file upload handlers
• Test for remote code execution vulnerabilities
• Look for admin panel access

Here's a comprehensive approach to secure your application:

1. Route Handling

Add this to your Global.asax.cs to handle unknown routes:

protected void Application_Error(object sender, EventArgs e)
{
    var exception = Server.GetLastError();
    if (exception is HttpException httpEx && httpEx.GetHttpCode() == 404)
    {
        // Log or handle suspicious 404s differently
        Logger.LogSuspiciousRequest(Request.Url.ToString());
        Response.Clear();
        Response.StatusCode = 404;
        Response.End();
    }
}

2. Request Filtering

Add this to your web.config:

<system.webServer>
  <security>
    <requestFiltering>
      <denyUrlSequences>
        <add sequence="muieblackcat" />
        <add sequence="cmd.exe" />
        <add sequence="wp-login.php" />
      </denyUrlSequences>
    </requestFiltering>
  </security>
</system.webServer>

3. Enhanced Logging

Create a custom ELMAH filter:

public class SuspiciousRequestFilter : IExceptionFilter
{
    public void OnException(ExceptionContext filterContext)
    {
        if (filterContext.Exception is HttpException httpEx)
        {
            var request = filterContext.HttpContext.Request;
            if (request.Url.AbsolutePath.Contains("muieblackcat"))
            {
                // Tag these specially in your logs
                Elmah.ErrorSignal.FromCurrentContext()
                    .Raise(new Exception("SUSPICIOUS REQUEST: " + request.Url));
            }
        }
    }
}

Set up alerts for patterns like:

• Multiple 404s for known malicious patterns
• Repeated requests to non-existent admin paths
• Attempts to access common exploit URLs

Consider using Application Insights or similar tools to track these patterns:

// In your Startup.cs
services.AddApplicationInsightsTelemetry();
services.AddApplicationInsightsKubernetesEnricher();

// Custom telemetry initializer
services.AddSingleton<ITelemetryInitializer, SuspiciousRequestTelemetry>();

1. Keep all frameworks and dependencies updated
2. Implement proper request validation
3. Configure custom error pages
4. Monitor your ELMAH logs regularly
5. Consider adding a WAF (Web Application Firewall)

---

When working with ASP.NET MVC applications, you might encounter unexpected requests to non-existent endpoints like "muieblackcat". The error typically appears as:

System.Web.HttpException: A public action method 'muieblackcat' was not found on controller...

These requests are typically from:

• Automated vulnerability scanners probing for known exploits
• Attempts to detect specific CMS platforms or frameworks
• Bots checking for outdated software with known security holes

The term "muieblackcat" appears to originate from certain exploit kits that target web applications. It's often associated with:

• SQL injection attempts
• Directory traversal probes
• Cross-site scripting (XSS) tests

Here are some effective countermeasures:

1. Custom Error Handling

Implement a global filter to handle 404 errors:

public class NotFoundHandler : IActionFilter
{
    public void OnActionExecuting(ActionExecutingContext filterContext)
    {
        if (filterContext.Result == null || filterContext.Result is HttpNotFoundResult)
        {
            // Log or block suspicious requests
            if (filterContext.HttpContext.Request.Url.AbsolutePath.Contains("muieblackcat"))
            {
                // Consider blocking the IP address
            }
        }
    }
}

2. Request Filtering in web.config

<system.webServer>
    <security>
        <requestFiltering>
            <denyUrlSequences>
                <add sequence="muieblackcat" />
            </denyUrlSequences>
        </requestFiltering>
    </security>
</system.webServer>

3. IP Blocking Strategy

For repeated offenders, implement IP blocking:

public class IPBlockAttribute : ActionFilterAttribute
{
    private static readonly ConcurrentDictionary<string, int> _accessAttempts = 
        new ConcurrentDictionary<string, int>();

    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        var ip = filterContext.HttpContext.Request.UserHostAddress;
        
        if (filterContext.HttpContext.Request.Url.AbsolutePath.Contains("muieblackcat"))
        {
            _accessAttempts.AddOrUpdate(ip, 1, (key, count) => count + 1);
            
            if (_accessAttempts[ip] > 3)
            {
                filterContext.Result = new HttpStatusCodeResult(403);
                return;
            }
        }
    }
}

Enhance your ELMAH configuration to specifically track these requests:

<elmah>
    <errorFilter>
        <test>
            <regex binding="Context.Request.ServerVariables['URL']" 
                   pattern="muieblackcat" />
        </test>
    </errorFilter>
</elmah>

• Keep your .NET framework and dependencies updated
• Implement rate limiting for your endpoints
• Consider using a Web Application Firewall (WAF)
• Regularly review your server logs for suspicious patterns