How to Create a Virus to Block Websites

Most of us are familiar with the virus that used to block Orkut and Youtube websites. If you are curious about creating such a virus on your own, here is how it can be done.

As usual I am using my favorite programming language ‘C’ to create thiswebsite blocking virus. I will give a brief introduction about this virus before I jump into the technical jargon.

This virus has been exclusively created in ‘C’. So, anyone with a basic knowledge of ‘C’ will be able to understand the working of this virus program. When this program is executed, it will block all those websites that are listed in the source code. In the following example, the sites that are listed in the source code are Google, Yahoo and Youtube. When you download the source code of this program, you have a choice to include your own list of sites that you want this virus to block.

I have just removed the source code of this program from this post as it is lengthy and makes the post look messy. You can still download the source code of this virus program from the following link:

Download Block_Site.rar

How Virus Program Works?

The Windows operating system maintains a special file called HOSTS which can be used to block any given hostname or domain name (website) by adding new entries onto it. This program works by modifying the HOSTS file by adding new entries of those sites that are intended to be blocked. The HOSTS file is located at:

%windir%\system32\drivers\etc (Usually: C:\windows\system32\drivers\etc)

So, when you execute this program, all it does is add the entries of the list of those sites (mentioned in the source code) to this HOSTS file. Once this is done, the site will be blocked from your computer. So, none of the browsers would be able to load those sites on your computer.

For more information on HOSTS file, I recommend reading my other post on How to use HOSTS file to block websites.

Now, as far as the technical part of this program is concerned, people who have a working knowledge of ‘C’ should be easily able to understand the working of this virus program. However, for those who are new to ‘C’ programming, here is the algorithm of this program:

• Determine the Root drive. ie: Find the drive (C:, D:, E: or F:) on which the Windows is installed.
• Navigate to: %windir%\system32\drivers\etc
• Open/Load the HOSTS file.
• Copy a list of those websites that are mentioned in the ARRAY to the END of the file.
• Save the file and Exit.

How to Compile the Source Code?

For a step-by-step compilation guide, refer my post: How to compile C Programs?

Testing the Virus:

1. To test, run the compiled module. It will block the sites that are listed in the source code.
2. Once you run the file block_Site.exe, restart your browser program. Then, type the URL of the blocked site and you’ll see the browser showing error “Page cannot displayed“.
3. To remove the virus type the following command in the Run.
   %windir%\system32\drivers\etc
4. There, open the file named “hosts” using the notepad. At the bottom of the opened file you’ll see something like this:
   127.0.0.1 google.com
5. Delete all such entries which contain the names of blocked sites.

6. How to Compile C Programs

   
   
   In many of my previous posts especially in the Programmingsection, I have used C as the programming language for writing the programs. If you’re new to C programming and find it difficult tocompile the C source codes then this post is for you.

   Here is a step-by-step procedure to install Borland C++ compiler 5.5 on your PC and compile the C programs.

   How to Install Borland C++ compiler?

   Follow the below steps to install Borland C++ compiler 5.5 on your PC:

   1. Download Borland C++ compiler 5.5 (for Windows platform) from the following link:
      Download Borland C++ 5.5
   2. After you download, run the file C++5.51.exe. The default installation path would be:
      C:\Borland\BCC55

   How to configure Borland C++ compiler?

   Here is a step-by-step instruction on how to configure the compiler:

   1. After you install Borland C++ compier, create two new Text Documents.
   2. Open the first New Text Document.txt file and add the following two lines into it:
      -I”c:\Borland\Bcc55\include”

      -L”c:\Borland\Bcc55\lib”
      Save changes and close the file. Now rename the file from New Text Document.txt tobcc32.cfg.
   3. Open the second New Text Document (2).txt file and add the following line into it:
      -L”c:\Borland\Bcc55\lib”
      Save changes and close the file. Rename the file from New Text Document (2).txt toilink32.cfg.
   4. Now copy the two files bcc32.cfg and ilink32.cfg, navigate to C:\Borland\BCC55\Bin and paste them.

   How to Compile the C Source Code (.C files)?

   Here is a detailed instruction on how to compile C source codes:

   1. You need to place the .C (example.c) file to be compiled in the following location:
   C:\Borland\BCC55\Bin
   2. Now go to the command prompt (Start->Run->type cmd->Enter)
   3. Make the following path as the present working directory (use the CD command):
   C:\Borland\BCC55\Bin
   4. To compile the file (example.c) use the following command:
   bcc32 example.c
   5. Now if there exists no error in the source code, you’ll get a compiled executable module (example.exe) in the same location (C:\Borland\BCC55\Bin).
   6. Now you have successfully compiled the source code into an executable file(.exe file).

NOTE: You can also change the ICON of the virus to make it look like a legitimate program. This method is described in the post: How to Change the ICON of an EXE file?