Securing .Net Core API with IP Blocking in C#

Our server may get requests from unwanted sources, it is difficult to moniter each and every IP and sources of requests.

We can Block specific IP addresses and Range of IP addresses and can make API secure.

Understanding the Importance of Securing API with IP Block List

Securing your API with an IP block list is essential to prevent malicious attacks, unauthorized access, and potential data breaches. By implementing an IP block list, you can restrict access to your API based on specific IP addresses, thereby enhancing the security of your system.

Benefits of Using an IP Block List

• Enhanced security: Prevent unauthorized access to your API
• Protection against malicious attacks: Block malicious IP addresses
• Regulatory compliance: Ensure compliance with data protection regulations
• Improved performance: Reduce server load by blocking unwanted traffic

Every Industry want to secure its data and servers from unauthorized peoples. Security team always moniters in suspicious activity from logs and try to restrict or apply measures to increase security.

IP block middleware is a security measure that can restrict access to a website or application based on the IP address of an incoming request.

Real time example

1. Preventing Unauthorized Access from Specific IPs

In this example we are going to block IP two 192.168.1.100", “192.168.1.101” so that request should not reach to server.

Use Case: A company wants to restrict access to its internal web application to only authorized IP addresses, ensuring that only users from within the company network can access it.

In this example we are going to block below IP address

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  var allowedIps = new List { "192.168.1.100", "192.168.1.101" }

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public class IpWhitelistMiddleware
{
    private readonly RequestDelegate _next;
    private readonly List _allowedIps;

    public IpWhitelistMiddleware(RequestDelegate next, List allowedIps)
    {
        _next = next;
        _allowedIps = allowedIps;
    }

    public async Task InvokeAsync(HttpContext context)
    {
        var remoteIp = context.Connection.RemoteIpAddress?.ToString();
        if (!_allowedIps.Contains(remoteIp))
        {
            context.Response.StatusCode = StatusCodes.Status403Forbidden;
            await context.Response.WriteAsync("Forbidden");
            return;
        }

        await _next(context);
    }
}

public void Configure(IApplicationBuilder app)
{
    var allowedIps = new List { "192.168.1.100", "192.168.1.101" };
    app.UseMiddleware(allowedIps);
}

Explanation

We are creating Custom Middleware which take IP addresses as input and we are checking IP address inside InvokeAsync method. we are returning Status403Forbidden if request came from blocklisted addresses.

Frequently Asked Questions

Q: How often should I update my IP block list?

A: It is recommended to update your IP block list at least once a week to stay ahead of potential threats.

Q: Can I whitelist certain IP addresses while using an IP block list?

A: Yes, you can whitelist specific IP addresses to allow them access to your API while maintaining the block list for others.

Conclusion

Securing your API with an IP block list is a critical step in safeguarding your data and preventing unauthorized access. By following the best practices outlined in this guide, you can enhance the security of your system and protect your valuable information from potential threats.