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Month: June 2012

Restrict access to website using IP address in IIS 7

We can restrict the access to a website using IP addresses or domain name in IIS 7 easily using the “IP and Domain Restrictions” module. Unlike IIS 6, this module is not enabled by default when you install Internet Information Services (IIS). we need to install it. But don’t worry, this can also be done easily through Server Manager.

You can follow the below step by step instruction:-


Enabling the “IP and Domain Restrictions” module

1. Open the Server Manager by selecting the path Start > Administrative Tools > Server Manager.

2. Click “Add Role Services” link to add the required Role. Check the “IP and Domain Restrictions” check box in “Select Role Services” screen and click “Next” to continue and complete the module installation. If the module is already installed, it will show as “installed”.




Configuring the “IP and Domain Restrictions” module


1. Start Internet Information Services (IIS) and open “IP and Domain Restrictions”.


Click to enlarge the image

Click to enlarge the image

2. Inside IPv4 Addresses and Domain Restrictions, select “Add Allow Entry” or “Add Deny Entry” to add Allow or Deny entries. You can specify IP address, an IP address range or a Domain Name.

Click to enlarge the image

Click to enlarge the image



3. For setting default policy, Click on “Edit feature settings” and select “Allow” or “Deny” as required.



Click to enlarge the image

Click to enlarge the image


1. Please note that configuring Allow or Deny restrictions using Domain name require reverse DNS look up every time a request arrives the server. Performing reverse DNS lookups is a potentially expensive operation that can severely degrade the performance of your IIS server.
2. IP entries are applied instantly without the need for a restart of the site or iis. The entries are processed in order so if you place deny and allow entries in the wrong order then you may lock the incorrect people out of the website.

Distributed Denial of service(DDOS)

A denial-of-service attack (DoS attack) or distributed denial-of-service attack (DDoS attack) is an attempt to make a computer or network resource unavailable to its intended users. The speciality of the DDOS is that, it relays attacks not from a single network/host like DOS. The DDOS attack will be launched from different dynamic networks which has already been compromised.


Ping of death :-
Attacker deliverately sending a ping packet, normally 64 bytes, that is larger than the 65,535 bytes. Many computer systems cannot handle an IP packet larger than the maximum IP packet size of 65,535, and often causes computer systems crash. A ping packet of size greater than 65,535, can be sent if it is fragmented.When a receiving computer reassembles the packet, a buffer overflow occurs, which often causes computer to crash.

Ping of flood:-
An attacker overwhelming the victim’s network with ICMP Echo Request (ping) packets. A flood of ping traffic can consume singificant bandwidth on low to mid-speed networks bringing down a network to a crawl.

Smurf Attack:-
Smurf attack exploits the target by sending repeated ping request to broadcast address of the target network. The ping request packet often uses forged IP address (return address), which is the target site that is to receive the denial of service attack. The result will be lots of ping replies flooding back to the innocent, spoofed host. If number of hosts replying to the ping request is large enough, the network will no longer be able to receive real traffic.

SYN Floods :-
When establishing a session between TCP client and server, a hand-shaking message exchange occurs betwen a server and client. A session setup packet contains a SYN field that identifies the sequence in the message exchange. An attacker may send a flood of connection request and do not respond to the replies, which leaves the request packets in the buffer so that legitimate connection request can’t be accommodated.

Teardrop Attack :-
Teardrop attack exploits by sending IP fragment packets that are difficult to reassemble. A fragment packet identifies an offset that is used to assemble the entire packet to be reassembled by the receiving system. In the teardrop attack, the attacker’s IP puts a confusing offset value in the sebsequent fragments and if the receiving system doesn’t know how to handle such situation, it may cause the system to crash.


1. Install Intrusion Detection System (IDS)
2. Implement Sysctl. Prevent ping attacks (ping of death, ping of flood, and smurf attacks) by disabling ping responses on the network machines. Enable IP Spoofing protection, and TCP SYN Cookie Protection.
3. Install advanced firewall and DDoS utilities.
4. Install Apache mod_evasive and mod_security modules to protect against HTTP DDoS attacks.

Since DDOS normally targets HTTP. Its always good to have a filtering system for apache . So that the request gets analyzed before web server handles it.

Detection is performed by creating an internal dynamic hash table of IP Addresses and URIs, and denying any single IP address from any of the following:

1. Requesting the same page more than a few times per second
2. Making more than 50 concurrent requests on the same child per second
3. Making any requests while temporarily blacklisted (on a blocking list)

1. Well there are no 100% prevention or protection against DDOS.
2. This steps won’t be enough if the DDOS attack is of very high volume.

How dns works

A DNS client “resolves” an IP address by sending a specially formatted request to a DNS server. The client has to know the address of one or more DNS servers in advance. The reply from the server may be a direct reply with the IP address associated with the hostname, a referral to another DNS server, or a response indicating the requested name can’t be found in DNS.

Typically, the request will ask the server to “recursive“, i.e. if it cannot answer the question from its own local memory, it should go ask other servers on behalf of the client. This behavior helps the local server build up its own cache of addresses frequently looked up.

Another form of query is called iterative query, where a client machine sends the request to a known DNS server , if that DNS server fail to resolve the domain name into a IP, then the client sends the request to another DNS and this process goes on and on until it get the required IP resolution by sending address resolution request to all its known DNS.If every known DNS fail to give the IP, then client goes to the root domain.

When you type a URL into your browser, it uses the following steps to locate the correct website:

A DNS client uses a resolver to request resolution of a host name to an IP address. The resolver is really just a special-purpose application that’s sole function is to act as an intermediary between name servers and various applications that need name resolution, such as Web browsers, e-mail applications, and so on. Here’s an example: Assume you fire up your browser and direct it to connect to www.mysite.com.

1. Your browser checks it’s cache (memory) to see if it knows which IP address the domain name resolves to. If it knows, it will resolve it and display the web page.
2. If the domain name is unable to be resolved, the browser will check your hosts file for a DNS entry.
3. If there’s no entry in the hosts file, the browser will check the default DNS server (specified via your computer’s network settings, /etc/resolv.conf). This is usually your ISP’s DNS server or your employer’s. If the default DNS server has an entry for that domain name, the browser will display the applicable website.
4. If the default name server has no cached results, it sends a DNS query to the root server for the .com domain.
5. The root server responds with the addresses of the name servers that are authoritative for the mysite.com domain.
6. Your ISP’s name server then builds another request for www.mysite.com and submits it to mysite.com’s name server, which responds with the IP address of www.mysite.com.
7. That information is passed back to your resolver, which passes it to your application.

How to install an SSL certificate on Ubuntu for Nginx


SSL (Secure Sockets Layer) is a protocol that provides secure communication over the internet. It uses cryptographic algorithms to encrypt data between the web server and the client’s browser. SSL is now deprecated, and TLS (Transport Layer Security) is the newer version that’s used widely.

In this tutorial, we’ll walk you through the steps to install and secure your website with SSL on Ubuntu 22.04 using Nginx. By the end of this guide, you’ll have a secure, encrypted connection between your web server and your users’ browsers, helping to ensure their safety and privacy.

Note: Originally, this blog was written for an old versions of Nginx and Ubuntu, I have updated to match the latest Ubuntu and Nginx recently.

Section 1: Installing Nginxon Ubuntu 22.04

Apache2 is a popular open-source web server software that plays a crucial role in hosting websites on the internet. In this section, we will walk through the process of installing Apache2 on Ubuntu 22.04.

Step 1: Update the Package List
Before installing any new software, it’s always a good idea to update the package list to ensure you are installing the latest version of the software. To update the package list, open the terminal on Ubuntu 22.04 and run the following command:

sudo apt update

Step 2: Install Nginx
Once the package list is updated, you can proceed with installing Nginx by running the following command:

sudo apt install nginx

This command will download and install Nginx along with all its dependencies. During the installation process, you will be prompted to confirm the installation by typing y and pressing Enter.

Enable and Start the Apache2 service

sudo systemctl enable nginx
sudo systemctl start nginx

Step 3: Verify NginxInstallation
To test if Nginx is working correctly, open a web browser and enter your server’s IP address or domain name in the address bar. You should receive the default Nginx landing page:

Congratulations, you have successfully installed Nginx on Ubuntu 22.04! In the next section, we will proceed with securing the web server by enabling SSL.

If you encounter any issues like Connection timeout or Unable to reach the website during the verification process, one possible cause could be that the Ubuntu firewall is blocking nginx traffic.

To check if Nginx is currently enabled in the firewall, you can use the Nginx is not listed as an allowed service, you can add it by running the following command:

sudo ufw allow 'Nginx Full'

This will allow both HTTP (port 80) and HTTPS (port 443) traffic to pass through the firewall, ensuring that your website is accessible to visitors.

Section 2: Installing SSL Certificate on Ubuntu 22.04 with Nginx

There are different types of SSL certificates, including domain validated, organization validated, and extended validation certificates. Each type has different features and provides varying levels of trust and security.

To install an SSL certificate on Ubuntu 22.04 with Nginx, you’ll need to follow these steps:

  • Obtain an SSL certificate: You can purchase an SSL certificate from a certificate authority (CA) or obtain a free SSL certificate from Let’s Encrypt. If you already have an SSL certificate, make sure it is valid and up-to-date.
  • Configure Apache2 to use the SSL certificate: Apache2 needs to be configured to use the SSL certificate for secure communication. This involves creating a virtual host for the SSL-enabled website, specifying the SSL certificate and key files, and enabling SSL encryption.

    You can read more about different SSL certificate types, the process to create a Certificate signing request(CSR), etc in the below blog post:

    SSL Certificates: What They Are and Why Your Website Needs Them

    Here are the steps for creating and configuring virtual hosts for Apache on Ubuntu 22.04:

    1. Create a new virtual host configuration file:

    sudo nano /etc/nginx/sites-available/linuxwebhostingsupport.in

    Add the following configuration to the file, replacing linuxwebhostingsupport.in with your own domain name:

    server {
        listen 80;
        listen [::]:80;
        server_name linuxwebhostingsupport.in;
        root /var/www/html/linuxwebhostingsupport.in/html;
        index index.html;
        location / {
            try_files $uri $uri/ =404;
    server {
        listen 443 ssl http2;
        listen [::]:443 ssl http2;
        server_name linuxwebhostingsupport.in;
        root /var/www/html/linuxwebhostingsupport.in/html;
        index index.html;
        ssl_certificate /etc/ssl/certs/linuxwebhostingsupport.in.crt;
        ssl_certificate_key /etc/ssl/certs/linuxwebhostingsupport.in.key;
        ssl_trusted_certificate /etc/ssl/certs/linuxwebhostingsupport.in_cabundle.crt;
        location / {
            try_files $uri $uri/ =404;

    Note: replace the paths to SSL certificate files with your own paths.

    2. Create the documentroot
    Run the following command to create the directory:

    sudo mkdir -p /var/www/html/linuxwebhostingsupport.in/html

    3. Test the Nginx configuration:

    sudo nginx -t

    If there are any issues, this check will show

    4. Enable the virtual host configuration file:

    If the configuration test is successful, enable the server block by creating a symbolic link in the /etc/nginx/sites-enabled directory:

    sudo ln -s /etc/nginx/sites-available/linuxwebhostingsupport.in /etc/nginx/sites-enabled/

    5. Create an HTML file named index.html in the new directory by running the following command:

    sudo nano /var/www/html/linuxwebhostingsupport.in/html/index.html

    This will open a text editor. Add the following code to the file:

            <title>Hello, world!</title>
            <h1>Hello, world!</h1>
            <p>Welcome to my website!</p>

    5. Reload Nginx for the changes to take effect:

    sudo systemctl reload Nginx

    Section 3: Testing SSL on Ubuntu 22.04 with Nginx

    Test your SSL configuration by visiting your domain in a web browser and verifying that the SSL certificate is valid and the website loads correctly over HTTPS. The browser should display a padlock icon and the connection should be secure

    You can also use the online tools like https://www.sslshopper.com/ssl-checker.html to check the configuration further. It can show if there any issues with certificate chain or trust.

    Section 4. Troubleshooting SSL on Ubuntu 22.04 with Apache2

    1. Certificate errors: If you encounter a certificate error, such as a warning that the certificate is not trusted or has expired, check the certificate’s validity and ensure it’s installed correctly. You can check the certificate’s details using your web browser, and make sure it matches the domain name and other relevant details.

    2. Mixed content warnings: If you see mixed content warnings, which indicate that some parts of the site are not secure, check for any resources that are still being loaded over HTTP instead of HTTPS. This can include images, scripts, and other files.

    3. SSL handshake errors: If you see an SSL handshake error, this usually means there’s an issue with the SSL configuration. Check your Apache configuration files and make sure the SSL directives are properly set up. You can also check for any issues with the SSL certificate, such as an invalid or mismatched domain name.

    4. Server configuration errors: If the SSL certificate is working properly, but the site is still not loading over HTTPS, check your server configuration files to make sure the VirtualHost configuration is correct. Make sure the correct SSL certificate and key files are specified and that the SSL directives are set up correctly.

    5. Browser-specific issues: If you’re only experiencing SSL issues in a specific web browser, make sure the browser is up to date and try clearing the cache and cookies. You can also try disabling any browser extensions that may be interfering with the SSL connection.

    Remember, troubleshooting SSL issues can be complex and may require some technical expertise. If you’re not comfortable with these steps or need additional help, it’s always a good idea to consult with a professional. You can contact me at admin @ linuxwebhostingsupport.in

    Section 5: Best Practices for SSL Configuration on Ubuntu 22.04 with Apache2

    Here are some tips and best practices for configuring SSL on Ubuntu 22.04 with Apache2:

    1. Keep SSL certificates up to date: Make sure to renew your SSL certificates before they expire. This can be done through the certificate authority where you purchased the certificate. Keeping your SSL certificates up to date will ensure that your website visitors are not presented with security warnings or errors.

    2. Configure Nginx for HTTPS-only access: To ensure that your website visitors are accessing your site securely, configure your Nginx server to only serve HTTPS traffic. This can be done by redirecting all HTTP traffic to HTTPS. To do this, add the red colored line to your server block of Nginx virtual host configuration file:

    server {
        listen 80;
        server_name linuxwebhostingsupport.in;
        return 301 https://$server_name$request_uri;

    3. Use secure ciphers and protocols: To protect the confidentiality and integrity of your website traffic, use secure ciphers and protocols. Disable weak ciphers and protocols such as SSLv2 and SSLv3. Use TLSv1.2 or higher, and prefer the use of forward secrecy. You can configure this in your Nginx virtual host configuration file by adding the following lines:

    ssl_protocols TLSv1.2;
    ssl_prefer_server_ciphers on;
    ssl_session_timeout 1d;
    ssl_session_cache shared:SSL:10m;
    ssl_session_tickets off;
    ssl_stapling on;
    ssl_stapling_verify on;

    Make sure to adjust the file paths and other configuration options to match your specific setup.

    You can find more detailed instruction on making your SSL configuration strong and best practices in the below post:

    Strong TLS/SSL Security on your server

    By following these best practices, you can ensure that your SSL configuration is secure and up to date.

    Section 6. Summary

    In this tutorial, we discussed how to install and configure SSL certificates on Ubuntu 22.04 with Nginx. We covered the different types of SSL certificates, the steps for obtaining and installing an SSL certificate, and how to configure Nginx to use the SSL certificate. We also discussed how to create virtual hosts for both SSL and non-SSL sites and how to troubleshoot SSL issues.
    It’s important to emphasize the importance of SSL for website security and user trust. SSL encryption helps protect sensitive information, such as passwords and credit card numbers, from being intercepted by attackers. Additionally, having a valid SSL certificate gives users confidence that they are interacting with a legitimate website and not an imposter.

    To follow best practices for SSL configuration, it’s recommended to keep SSL certificates up to date, configure Nginx for HTTPS-only access, and use secure ciphers and protocols. By following these best practices, website owners can help ensure the security and trustworthiness of their website.

  • Case insensitive url Aapche Webserver

    How to enable Case-Insensitive url’s ?

    Webserver: Apache

    OS: Linux

    One of our customer had opened ticket. He has a very interesting need. He wants his site urls  to be Case-insensitive . I will explain with examples:- He needs the following urls to work currently he is getting 404 errors for each request.



    We were unable to add rewrite rules in his htaccess files as we need to write rule for every single file that has a mixture of upper and lower case.

    http://yourdomain.com/yourpage.html => This is the correct url

    He needs this url http://yourdomain.com/Yourpage.html to load even if they have one spelling mistake or there is one capitalization error. This was found very strange. We have managed to fix the issue by adding an apache module server wide, which neutralise all the the upper case and lower case characters to a single format.

    Solution: If you want requested URLs to be valid whether uppercase or lowercase letters are used and with one spelling mistake, “mod_speling” module needs to be enabled in apache.

    The mod_speling module is part of the standard Apache distribution but is not enabled by default, so you need to explicitly enable it. When mod_speling is installed, it may be turned on for a particular scope (such as a directory, virtual host, or the entire server) by setting the CheckSpelling directive to On.

    For making URL case-insensitive in cPanel:

    First run belwow on Cpanel based server : /scripts/easyapache And select ‘Spelling’ from the available module list for apache. Once apache/php are recompiled with this option and easyapache finishes, you can put below code in the .htaccess or in the virtual host entry of the particular domain to apply it to any directory/directories :

    < IfModule mod_speling.c > CheckCaseOnly On CheckSpelling On < / IfModule > This helped to fix this particular issue

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